Heating element? (3)

I believe the answer is:

tin

I'm a little stuck... Click here to teach me more about this clue!

'element' is the definition.
(tin is a kind of element)

'heating' is the wordplay.
'TIN' is hidden in amongst the letters.
But, I'm uncertain how the hidden word is indicated.

Can you help me to learn more?

(Other definitions for tin that I've seen before include "Earnings" , "Metal in Argentina" , "A silvery-white metal, symbol Sn" , "Kind of metal often used as food container" , "Silver-white element often used in food containers" .)

I've seen this clue in the Evening Standard.

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