Sarcastic wordplay by fellow (7)
I believe the answer is:
pungent
'sarcastic' is the definition.
(similar in meaning)
'wordplay by fellow' is the wordplay.
'wordplay' becomes 'pun' (synonyms).
'by' is a charade indicator (letters next to each other).
'fellow' becomes 'gent' (synonyms).
'pun'+'gent'='PUNGENT'
(Other definitions for pungent that I've seen before include "Incisive" , "Strong and sharp" , "Biting" , "Acrid - painful" , "delivering powerful smack" .)