Good FCP audio filter primer
I use Logic for all my audio. I have not used any of the FCP filters.
For audio editing one really needs to start with good quality reference monitors and a/d/a converters so they can actually hear what’s there before much time is spent working on it. Also a conservative amount of EQ can make a world of difference.
If you’re limited to the native filters, I would suggest trying any one or a combination of the 3-Band EQ, the expander/noise gate and/or the low-pass(aka treble-cut).
Hope this helps.
“Patience Luke, let the object of your desire come to you” — Obi-Wan Kenobi