Crossword Genius

Wow greats by cooking Oz sausage (7,3)

Ross

I believe the answer is:

mystery bag

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'oz sausage' is the definition.
I don't know anything about this answer so I cannot judge whether this works.

'wow greats by cooking' is the wordplay.
'wow' becomes 'my' (both can be expressions of surprise).
'cooking' is an anagram indicator (letters cooked up into a new form).
'greats'+'by'='greatsby'
'greatsby' anagrammed gives 'sterybag'.
'my'+'sterybag'='MYSTERY BAG'

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