Horse coat color (4)
I believe the answer is:
roan
'horse coat color' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for roan that I've seen before include "Horse with reddish-brown coat" , "Horse with coat speckled with white or grey" , "Bay horse with white/grey hairs in its coat" , "Horse with main colour interspersed with hairs of another" , "nag" .)