Sorrel horse (4)
I believe the answer is:
roan
'sorrel horse' 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 "Horse with reddish-brown coat" , "(Horse) white-sprinkled coat" , "Red-coloured horse" , "Horse with brownish coat speckled with white" , "Horse with coat speckled with white or grey" .)