Crossword Genius

Foul gas given off by knitted cardigans (6)

Ross

I believe the answer is:

rancid

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'foul' is the definition.
(I've seen this in another clue)

I don't understand how the remainder of the clue works.

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(Other definitions for rancid that I've seen before include "Tasting or smelling sour, butter say" , "Rank, high" , "Rotten; high" , "No longer fresh" , "Sour, rotting" .)

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