Horse in stud's outside, glittering (8)

I believe the answer is:

sequined

'glittering' is the definition.
(sequins sparkle or glitter)

'horse in stud's outside' is the wordplay.
'horse' becomes 'equine' (equine means a horse or related animal).
'in' means one lot of letters goes inside another.
'outside' suggests removing the centre.
'stud' with its centre taken out is 'sd'.
'equine' placed within 'sd' is 'SEQUINED'.

(Another definition for sequined that I've seen is " Of clothes, covered with ornamental spangles".)

I've seen this clue in The Guardian.

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