You could manufacture one the old fashioned way by duplicating the layer, darkening it, blurring it, offsetting it; but I think Brendan Gibbons has made a free effect that will do this. If you search for him on this forum or search the effects at fcp.co you should find it.
All the best,
Tom
Class on Demand DVDs “Complete Training for FCP7,” “Basic Training for FCS” and “Final Cut Express Made Easy”
Coming in 2012 “Complete Training for FCPX” from Class on Demand
“Final Cut Pro X for iMovie and Final Cut Express Users” from Focal Press