Chemical substance that provides heat (7)

I believe the answer is:

element

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This clue might be a double definition.

'chemical' is the first definition.
(thesaurus)

'substance that provides heat' is the second definition.
'element' can be an answer for 'substance' (element is a kind of substance). I am unsure of the rest of the definition.

Can you help me to learn more?

(Other definitions for element that I've seen before include "Eg, one dn" , "Iron, for instance - part of an electric kettle" , "Fundamental part of whole" , "Trace" , "Constituent of universe" .)

I've seen this clue in The Daily Express.

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