Assuming that the video and audio are both from the same shot, R click on the audio event and select from the context window that opens 'Add Missing Stream for Selected Event'. The matching video for that audio selection will then be added to a new video track just above the audio track. You can then create a new subclip if you wish to do so. If the audio is not directly associated with the video, then you will need to go back to the original video event and create a new subclip to the length that you now require. When creating subclips, consider making them over-length in order to allow for a bit of wriggle room later on.

Adding just the video or audio stream from an event can be done in a number of ways. One way is to hold down the R button on the mouse when dragging an event onto the timeline. After releasing the R button, a context window will open which gives a choice of how and what is wanted to be added to the timeline, including V or A only.

You can also ungroup the audio from the video on the timeline by highlighting the event and hitting the 'U' key on the keyboard. If you want to delete the audio or video portion of the event only, just make sure that only the audio or video event is highlighted and then delete. To regroup the audio and video, highlight both the audio and video events and then hit the 'G' key on the keyboard.

Nearly a year ago, Vegas Creative Software created 4 x 30 mins tutorials covering the basics of Vegas Pro (version 17 as that was the current version at the time). These are on YouTube and the first one is at

Heaps of other Vegas Pro How To videos on YT as well.

Most helpful thank you.
It was a bit of trial and error to find the exact frame I needed to butt to the end of the clip. I didn't want to put the clip on the timeline as I already had clips on the timeline to follow the clip I wanted to extend, so I cut it in the Trimmer window. I thought I knew which frame was the last one on the timeline, 471, so in theory I needed from 472, but the source clip in the Trimmer window showed totally different frame numbers and so i had to guess where to cut. A bit imprecise.
In Media Composer if you want to find the Source clip you just park the playhead on the frame in the Record or Preview monitor, hit Match Frame and that exact frame comes up in the Source or Trimmer monitor no matter which bin it resides in and you do what you want from there.
I'll adjust 🙃.

@alan-c Meant to say, when you select the audio or video part of an event, if there are any other items “grouped” to it, they will get a faint bluish colour around the frame. If the item you select doesn’t cause this to happen then it’s not grouped, it is already Ungrouped. Selecting multiple items and pressing G will Group them together.

Thanks Dexcon, I didn't see your post till after I'd posted.
The audio is a music track, not associated with the clip, so in that case re subclipping would be the idea.
Yes, I see that leaving extra room in the subclip is a good idea in this case where it's not so easy to extend.
Thanks for the tutorial tip.

@alan-c
Here are a number of basic tutorials that have been created with an earlier version of Vegas Pro, but very well the way of working in Vegas Pro:
(Attention: You must use the link in the first line to continue to get)
https://www.vegascreativesoftware.info/de/tutorials/vegas-pro-basic-tutorial-by-andrew-devis-based-on-sony-vegas-pro-12--106007/

Of course this advice doesn't apply to every case, but GENERALLY speaking, editors usually lay down A-roll and primary audio tracks first, then edit-in B-roll on top to help avoid the very issue you seem to be having.

Based on your description, it sounds to me like you're trying to wag the dog by its tail with the way you created your sub-clips.

Here are more tutorials and resources:

https://www.vegascreativesoftware.info/us/forum/got-questions-consult-the-tutorials-first-please--120282/

If it's not very far, just hold down the CTRL key when you make it longer to fit. It will slow it down a little but but you'll use exactly the segment you wanted to use without having to add more video.

Thank you one and all for the help. I have bookmarked the tutorial information suggested, and so that will keep my head down for quite a while I expect.
I have to say that it surprises me that after thirteen years or so of editing experience, starting with Pinnacle Studio 8, then to Liquid Edition, (a very underrated program), and Media Composer 6, I sit in this chair with Vegas Pro on the screen feeling like a total beginner! It's just that things are done so differently. I'm sure I'll get a roll on once I explore these tutorials and get back to basics.
I appreciate your help and your patience.

Of course this advice doesn't apply to every case, but GENERALLY speaking, editors usually lay down A-roll and primary audio tracks first, then edit-in B-roll on top to help avoid the very issue you seem to be having.

Based on your description, it sounds to me like you're trying to wag the dog by its tail with the way you created your sub-clips.

Thank you.
You may well be right, but to clarify, there was no A-roll required here, this was just a simple exercise to begin experimenting with Vegas, mostly drone footage to send to grandchildren 🙂. Some of the source clips were quite long, so in Avid I would often preview long clips and subclip them so that I had shorter, more relevant material in a bin to draw from. I find it a very useful workflow method.
However, in Avid the subclips are not set in stone. If I send a subclip to the timeline, on top of my music bed, and the clip is a little short for the passage in the music, I would just drag the end of the clip out to the next marker and the extra material is simply borrowed back from the source material. Bam, done, 2 seconds, move on. Obviously it's one of the many things I'm going to find works differently in Vegas.
The audio issue was a very simple fix which was pointed out to me.
Thanks again.