A year or two ago, I would have said hands down, iZotope RX Advanced (part of their RX Post Production bundle) was number one. But today a number of new noise reduction apps have appeared. I think I have 5 or 6 total. IMHO, the easiest to use are Waves’ Clarity Vx and Accentize’s dxRevive. They are terrific for cleaning dialogue tracks, basically one-knob solutions. dxRevive is almost magical, as not only does it remove noise, but reintegrates missing frequency components. It deals with broadband noise, clipping, clicks & pop, and reverb. The basic versions cost about $30. There are also Pro versions which have a few more features, and in the case of dxRevive an addition denoise model, but the basic engine is the same. I’ve seen a couple reports that FCP has problems with Clarity Vx, but it works fine for me with Sonoma 14.1.2, MacBook Pro, M2Max, 32GB RAM, 2TB SSD.