Hurtful remark (4)
I believe the answer is:
barb
'hurtful remark' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for barb that I've seen before include "Backward-facing part of hook" , "A thorn or a gibe" , "Pointed part - gibe" , "Backward projecting point of an arrowhead" , "Arrowhead projection" .)