Brawl’s beginning after pub remark that’s hurtful (4)
I believe the answer is:
barb
'remark that's hurtful' is the definition.
'brawl's beginning after pub' is the wordplay.
'beginning' suggests taking the first letters.
'after' means one lot of letters go next to another.
'pub' becomes 'bar' (I've seen this before).
The initial letter of 'brawls' is 'b'.
'b' put after 'bar' is 'BARB'.
(Other definitions for barb that I've seen before include "added to wire?" , "Thorn or spike" , "Part of an arrow head" , "Woundingly pointed remark" , "Sharp projection" .)