Use moderate wordplay with sarcasm (9)
I believe the answer is:
pungently
'use moderate wordplay with sarcasm' is the definition.
I can't tell whether this defines the answer.
'wordplay with sarcasm' is the wordplay.
'wordplay' becomes 'pun' (synonyms).
'with sarcasm' becomes 'gently' (I can't explain this - if you can you should give a lot more credence to this answer).
'pun'+'gently'='PUNGENTLY'
Can you help me to learn more?
(Other definitions for pungently that I've seen before include "With sarcasm!" , "caustic way" .)