Residual traces of vile gas are destroyed with it (9)

I believe the answer is:

vestigial

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'residual traces of vile gas are destroyed with it' is the definition.
I can't judge whether this definition defines the answer.

'vile gas are destroyed with it' is the wordplay.
'are destroyed with' is an anagram indicator.
'vile'+'gas'='vilegas'
'vilegas' with its letters mixed up with 'it' gives 'VESTIGIAL'.

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(Other definitions for vestigial that I've seen before include "not completely developed" , "remnants" , "garment worn by single girl touring island" .)

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

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