[Geoffrey Maclean]

Answer for Final Cut Pro 10 – to unlink audio from a video clip to drag audio only into timeline.

(i) Highlight the video clip in the library that has the audio you want to use. (ii) go to the drop box immediately below the library on your computer screen, to the right of the ‘key’ symbol, and select audio only. (iii) drag the video clip you have highlighted into the timeline, you will see only the audio is being dragged into the timeline.

It worked for me and I hope it works for you.