Horse galloped round ring (4)
I believe the answer is:
roan
'horse' is the definition.
(roan is a kind of horse)
'galloped round ring' is the wordplay.
'galloped' becomes 'ran' (I've seen this in other clues).
'round' means one lot of letters goes inside another.
'ring' becomes 'o'.
'ran' placed around 'o' is 'ROAN'.
(Other definitions for roan that I've seen before include "Horse with main colour interspersed with hairs of another" , "Horse with reddish-brown coat" , "nag" , "Red-coloured horse" , "Two-colour horse" .)