Amused expression shown by timeless group in circle of light (4)

I believe the answer is:

halo

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'circle of light' is the definition.
(I've seen this in another clue)

I can't explain the rest of the clue.

(Other definitions for halo that I've seen before include "glory" , "Aura representing saintliness" , "Luminous ring" , "Light around sun, saint" , "Angelic aura" .)

I've seen this clue in The Independent.

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