Garments in wide, upright box (5)
I believe the answer is:
wraps
'garments' is the definition.
(wrap is a kind of garment)
'wide upright box' is the wordplay.
'wide' becomes 'w' (abbreviation e.g. in cricket).
'upright' is a reversal indicator (in a down clue, letters go up).
'box' becomes 'spar' (sparring is a kind of boxing).
'spar' reversed gives 'raps'.
'w'+'raps'='WRAPS'
'in' acts as a link.
(Other definitions for wraps that I've seen before include "Loose garments; finishes filming" , "Secret things are kept under them" , "Envelops" , "Fillings rolled up in soft tortillas" , "Winds" .)