Horse hue (4)
I believe the answer is:
roan
'horse hue' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for roan that I've seen before include "Reddish-coloured horse" , "Horse with a coat of mixed colour" , "(Horse) white-sprinkled coat" , "Type of 17's coat colouring" , "Horse with brownish coat speckled with white" .)