Mythical winged horse (7)
I believe the answer is:
pegasus
'mythical winged horse' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for pegasus that I've seen before include "fabulous horse" , "Mount flying" , "Winged horse - constellation" , "Immortal winged horse of Greek mythology" , "high horse" .)