Wild mountain goat (4)
I believe the answer is:
ibex
'wild mountain goat' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ibex that I've seen before include "Mountain goat with long curved horns" , "being nimble-footed" , "Mountain-goat" , "Wild goat of North Africa" , "Large-horned mountain goat" .)