Sleeveless jerkin (6)
I believe the answer is:
tabard
'sleeveless jerkin' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for tabard that I've seen before include "Short sleeveless tunic" , "Jerkin; heraldic coat" , "Knight's outer tunic" , "Herald's garment" , "Short tunic, open at the sides" .)