Surely not live rat in an air freshener! (10)

I believe the answer is:

ventilator

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'an air freshener' is the definition.
The definition suggests a singular noun which matches the answer.

'surely not live rat' is the wordplay.
'not live rat' anagrams to 'VENTILATOR'.
However, I'm unsure how this is indicated.

'in' is the link.

Can you help me to learn more?

(Other definitions for ventilator that I've seen before include "Opening to allow air flow" , "apparatus to assist breathing" , "Machine for artificial respiration" , "Fan" , "breather" .)

I've seen this clue in The Globe and Mail.

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