Crossword Genius

Unexpected blow for straw user? (6,5)

Ross

I believe the answer is:

sucker punch

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'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" .)

I've seen this clue in The Telegraph.
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