Cowboy boot accessory (4)
I believe the answer is:
spur
'cowboy boot accessory' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for spur that I've seen before include "Branch - incitement" , "Goad, prod" , "Goad - branch line" , "Spike on a horse-rider's boot" , "Goad as for use by horse-rider" .)