I realize I might not have been clear. Years ago, before FCP, there was NewTek's Toaster. To save valuable HD space, when finished with a project, you could have toaster reference every clip in the timeline and automatically delete everything you did not use. This was an automatic function and it would not only delete footage you didn't use, but any clips you did use would be trimmed to the in and out point established in the timeline. Does FCP have something similar?
Also in the future when posing it is best to put something descriptive of your question for the subject. You simply put final cut pro. This whole forum is about final cut pro. Putting something like getting rid of unuded media not only lets people who might be able to help what your question is about. A lot of people will save themselves time and just skip over questions they know they cannot answer well. In addition it REALLY helps those searching the forums if there is a good basic description of what the question will be about in the subject line.
[Tim Lindop]"Is there a button I can push that would result with my footage deleted except that used in a selected time-line?"
Tu put that function in a button, would be very dangerous.
You can use Media Manager to separate the footage you have used in a project/sequence. Then you can delete the rest.