Feral horse (7)
I believe the answer is:
mustang
'feral horse' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for mustang that I've seen before include "Small feral horse of the US" , "Wild horse of the West" , "Small, half-wild horse of the U.S." , "Wild or half-wild horse" , "Hardy wild horse of the American western plains" .)