Strawberry horse (4)
I believe the answer is:
'strawberry 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 with brownish coat speckled with white" , "Horse - leather" , "Horse with a coat of mixed colour" , "Nora (anag) - horse" .)