Unexpected blow for straw user? (6,5)
I believe the answer is:
sucker punch
'unexpected blow' is the definition.
(I've seen this before)
'straw user?' is the wordplay.
'straw' becomes 'sucker' (a straw is used to suck a drink).
'user?' becomes 'punch' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'sucker'+'punch'='SUCKER-PUNCH'
'for' is the link.
Can you help me to learn more?
(Other definitions for sucker punch that I've seen before include "Sudden setback - surprise blow from behind" , "Surprise attack" , "blow unexpectedly" , "Sudden unexpected blow" .)