Yes, do you have any extra 3rd Party Plug Ins for FCP - some of them are really great, better than the FCP build in ones.
In any case, go in the Generator Tab in your viewer and find it under "Render".
Use a wipe with a very feathered edge between sharp and blurred footage.
Or duplicate your footage, and blur the copy. Then use a B&W grad matte to control how/where the blurred footage composites thru the sharp footage.