Loudly regret returning after tea with posh driver (9)

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

FF (in musical notation, ff = Italian fortissimo = instruction to play very loudly) + RUE (regret) reversed (returning), after CHA (slang for tea, from Asian languages) + U (posh, as in “U and non-U”).