Forming a habit to ignore cold food ingredient (8)

I believe the answer is:

additive

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'ingredient' is the definition.
(I've seen this before)

I cannot understand how the remainder of the clue works.

(Other definitions for additive that I've seen before include "Substance put into food" , "Produced by summing" , "Supplement" , "Colouring maybe" , "Something joined, to food say" .)

I've seen this clue in The Guardian.

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