Beer, big hit (6)
I believe the answer is:
wallop
I believe this clue is a double definition.
'beer' is the first definition.
(I've seen this before)
'big hit' is the second definition.
(I've seen this before)
(Other definitions for wallop that I've seen before include "Strike very hard" , "Beer - hit hard" , "Punch" , "Severe blow" , "A heavy resounding blow (6)" .)