You drag the movie clip from the explorer pane onto the workspace. When you click the button that was created, the movie plays. That's about as tough as it gets.
Render the small clip as it's own MPEG file. Then, rather than dragging the main movie onto the workspace pane, drag the main movie onto the project view pane and drop it on the DVD icon. Drag the clip onto the workspace. You now have a button pointing to the small clip. Double click on the small clip button to navigate into it. Set the end action of the clip to link to the main movie.