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.
'DON' can be found hidden inside '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" .)