Crossword Genius

Ferns, if rotten, something that smells (7)

Ross

I believe the answer is:

sniffer

'something that smells' is the definition.
(something that sniffs)

'ferns if rotten' is the wordplay.
'rotten' indicates an anagram.
'ferns'+'if'='fernsif'
'fernsif' is an anagram of 'SNIFFER'.

I've seen this clue in The Times.
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