I know Avid has a filter to resize the aspect ratio for a clip that is full frame 4x3, to the right (and original) 16x9 size. Does FCP have this or is it a manual go in and resize?
Are you talking about stretching an anamorphic signal back out to 16:9?
You can mark the clip, in the browser, as anamorphic (scroll through the clip settings until you find it), and FCP will automatically display it as 16:9 in the clip viewer. Open an anamorphic time line and drop the clip in and it will work just fine. No need to apply filters of any kind.
sorry to make this confusing... it is full frame (4x3) that was originally 16x9 that needs to get shrunk back to letterbox in a 4x3 frame (rest of show is 4x3). It is from a DVD that was made wrong, but is just for reference until the real clips come in - which will be 16x9 HDV.