These are collarless, fitted and they might keep you warm (5,5)

I believe the answer is:

solar cells

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'they might keep you warm' is the definition.

'these are collarless fitted' is the wordplay.
'collarless' can be anagrammed to 'SOLAR CELLS'.
But, I'm unsure how this is indicated.

'and' acts as a link.

Can you help me to learn more?

(Another definition for solar cells that I've seen is " energy suppliers".)

I've seen this clue in The Everyman puzzle in The Observer.

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