Currently Being ModeratedJan 18, 2013 10:25 PM (in response to explorz)
Set the start and stop times where you want them. Use the command File > Create New Version to create a new (shorter) version. Then go back into the original and unset the start and stop.
To avoid confusion, find the new (shorter) one in your iTunes library, and edit its info so that you can tell them apart. A common convention is "Title (edit)" but you can use whatever you want.
You will end up with both versions in your library.