Neat Video makes a noise reduction plugin for FCPX (not sure if they have updated it yet for 10.1 but you can google it). Personally, I use the Denoiser filter from Tiffen which is part of the DFX3 packages they offer.
from innobits.com. It is stand-alone and it hasn't been updated for over three years but the results are still good. Google for reviews. May not work for you but it's an option you might want to consider.