Horse coloring (4)
I believe the answer is:
roan
'horse coloring' 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) white-sprinkled coat" , "Horse - leather" , "Two-colour horse" , "Horse with brownish coat speckled with white" , "Horse with a coat of mixed colour" .)