'Please leave' picked up very loudly from football supporter? (7)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

FF (abbreviation for fortissimo = musical term for very loudly) + OF FAN (from a football supporter, for example), all reversed (picked up = upwards in a down clue). Slang expression meaning “go away!”, but rather less polite than the “please” in the definition implies.