Strong punch that would make you croak? (6,4)

I believe the answer is:

deadly blow

'that would make you croak?' is the definition.
(croak can informally mean to die)

'strong punch' is the wordplay.
'strong' becomes 'deadly'.
'punch' becomes 'blow'.
'deadly'+'blow'='DEADLY BLOW'

I've seen this clue in The Guardian.

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