Uniform jacket (5)
I believe the answer is:
tunic
'uniform jacket' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for tunic that I've seen before include "Dress for soldier" , "Policeman may be in one" , "Military uniform" , "Upper garment, for a soldier say" , "Loose fitting light cloak extending to the hip or lower" .)