While FCPX does not yet have a de-noising effect (as of version 10.2.2) it does contain an effect called Add Noise. Despite its name I was able to use the effect to clean up a great deal of noise in one of my clips. Add Noise allows you to add five types of noise, one of which is Pink Noise. For some reason selecting Pink Noise eliminated most of the noise in my clip. I also set blend to normal, amount to 0 and opacity to 100. I have no idea why this works but I thought someone else might find this useful.