Crossword Genius

Forgiving zip on first case? (7,4)

Ross

I believe the answer is:

patient zero

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'first case?' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.

'forgiving zip on' is the wordplay.
'forgiving' becomes 'patient' (I've seen this before).
'zip' becomes 'zero' (synonyms).
'on' says to put letters next to each other.
'patient'+'zero'='PATIENT ZERO'

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I've seen this clue in the Sydney Morning Herald.
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