Blow a fair share? (5)

I believe the answer is:

whack

I believe this clue is a double definition.

'blow' is the first definition.
(whack is a kind of blow)

'a fair share?' is the second definition.
(as in a fair whack)

(Other definitions for whack that I've seen before include "ration" , "Strike sharply" , "Strike; share (slang)" , "Punch" , "Hit loudly" .)

I've seen this clue in The Times.

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