Old and grim smell (5)

I believe the answer is:

odour

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'smell' is the definition.
(I know that smell can be written as odour)

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

(Other definitions for odour that I've seen before include "Stench" , "for the nose to detect" , "Aroma or fragrance" , "Bouquet" , "essence" .)

I've seen this clue in The Sun.

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