Possibly to cover a garment (8)
I believe the answer is:
overcoat
'garment' is the definition.
(overcoat is a kind of garment)
'possibly to cover a' is the wordplay.
'possibly' indicates anagramming the letters.
'to'+'cover'+'a'='tocovera'
'tocovera' with letters rearranged gives 'OVERCOAT'.
(Other definitions for overcoat that I've seen before include "Ulster, for example" , "Inverness" , "Clobber" , "protective layer" , "Evocator (anag.)" .)