Mistake about a garment (8)

I believe the answer is:

slipover

'a garment' is the definition.
(slipover is a kind of garment)

'mistake about' is the wordplay.
'mistake' becomes 'slip' (a slip is a blunder or mistake).
'about' becomes 'over' (both can mean around).
'slip'+'over'='SLIPOVER'

(Other definitions for slipover that I've seen before include "Top" , "knitted garment" .)

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