Hurtful; sarcastic (7)
I believe the answer is:
cutting
I believe this clue is a double definition.
'hurtful' is the first definition.
(I've seen this before)
'sarcastic' is the second definition.
(thesaurus)
(Other definitions for cutting that I've seen before include "(Of a remark) hurtful" , "Channel" , "Wounding" , "Barbed" , "Sharp (remark); piece kept from paper" .)