Baku improved, taking in royal garment (5)
I believe the answer is:
burka
'garment' is the definition.
(I know that burka is a type of garment)
'baku improved taking in royal' is the wordplay.
'improved' indicates anagramming the letters.
'taking in' indicates putting letters inside.
'royal' becomes 'r' (common abbreviation e.g. RM - Royal Marine).
'baku' anagrammed gives 'buka'.
'buka' placed around 'r' is 'BURKA'.
(Other definitions for burka that I've seen before include "Muslim woman's garb" , "Afghan women's covering" , "Muslim garment (K not Q)" , "Loose garment worn by Muslim women" , "it's on some Muslims" .)