The man's a bit of a sophist (3)
I believe the answer is:
his
'the man's' is the definition.
(thesaurus)
'a bit of a sophist' is the wordplay.
'a bit of' indicates the answer is hidden within the clue (I've seen 'a bit' mean this (the answer is formed by a bit of the clue)).
'HIS' is hidden in the letters of 'sophist'.
(Other definitions for his that I've seen before include "Belonging to that man" , "That man's" , "that chap's" , "To - Coy Mistress (Marvell)" , "It belongs to him" .)