Export the audio track(s) from Final Cut. Double click the track(s) in the waveform/timeline to edit it. Drag over a part that just has the high pitch noise and select noise sample or something like that. I don't have it open so the terms and names are perhaps incorrect. Then find and select denoise. I suggest that you also try applying the denoise filter and try one of the presets by listening and selecting. It has saved audio, I thought was unuseable.
One more thing: STP imports the entire clip so if the audio comes from a long clip, you can drag over and cut or delete the unused parts in the original timeline before double-clicking it.
Can someone tell me how to cut a minute out of a sequence when I feel it's cut perfect the way it is.