The horse galloped out of the ring (4)
I believe the answer is:
roan
'the horse' is the definition.
(roan is a kind of horse)
'galloped out of the ring' is the wordplay.
'galloped' becomes 'ran' (I've seen this in another clue).
'out of' means one lot of letters goes inside another (some letters on the outside of others).
'the ring' becomes 'o' (O is the shape of a ring).
'ran' enclosing 'o' is 'ROAN'.
(Other definitions for roan that I've seen before include "Horse with main colour interspersed with hairs of another" , "Type of 17's coat colouring" , "Horse - leather" , "Horse with a coat of mixed colour" , "Nora (anag) - horse" .)