Preserve hot water? (3)

I believe the answer is:

jam

I believe this clue is a double definition.

'preserve' is the first definition.
(jam is a kind of preserve)

'hot water?' is the second definition.
(thesaurus)

(Other definitions for jam that I've seen before include "Spread; improvise (jazz)" , "Conserve" , "Preserve - predicament" , "Sweet stuff for bread - stuff it in" , "Block signals" .)

I've seen this clue in The Times.

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