A piece of silk I monopolise for garment (6)

I believe the answer is:

kimono

'for garment' is the definition.
(kimono is a kind of garment)

'a piece of silk i monopolise' is the wordplay.
'a piece of' says the answer is hidden in the clue.
'KIMONO' can be found hidden inside 'silk i monopolise'.

(Other definitions for kimono that I've seen before include "wrapper" , "Jap. wrap" , "Long loose Japanese robe" , "dressing-gown" , "Woman's loose robe, tied with a sash" .)

I've seen this clue in The Guardian.

Want a hint initially instead of a full solution? Install my app