He’s a bit of a hedonist (3)
I believe the answer is:
don
'he's' is the definition.
'a bit of a hedonist' is the wordplay.
'a bit of' says the answer is hidden in the clue (I've seen 'a bit' mean this (the answer is formed by a bit of the clue)).
'DON' is hidden in the letters of 'hedonist'.
(Other definitions for don that I've seen before include "and 13 Down: Mozart opera" , "A Mafia chief like Corleone" , "Nod off like Mafia chief" , "Spanish gentleman" , "Yorkshire river" .)