Decorative line (6)
I believe the answer is:
stripe
'decorative line' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for stripe that I've seen before include "Narrow band of colour" , "Band of colour, maybe of rank" , "Chevron on a uniform to denote military rank" , "Sleeve badge showing military rank" , "Braid showing military rank" .)