Chat about small sources of illumination (9)

I believe the answer is:

gaslights

'sources of illumination' is the definition.

'chat about small' is the wordplay.
'chat' becomes 'gas' (informal term meaning to chat).
'about' means one lot of letters goes inside another.
'small' becomes 'slight' (I've seen this before).
'gas' enclosing 'slight' is 'GASLIGHTS'.

(Another definition for gaslights that I've seen is " Shiners".)

I've seen this clue in The Times.

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