One thing that stays hot in the fridge (7)

I believe the answer is:

mustard

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'one thing that stays hot in the fridge' is the definition.
The definition suggests a singular noun which matches the answer.

This is the entire clue.

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(Other definitions for mustard that I've seen before include "Pungent powder or paste" , "Hot-tasting seed" , "Murderer" , "Pungent condiment" , "The keen stuff ?" .)

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

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