Large-horned mountain goat (4)
I believe the answer is:
ibex
'large-horned mountain goat' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for ibex that I've seen before include "Wind goat of North Africa" , "Sure-footed type" , "Large-horned wild goat" , "being nimble-footed" , "one used to high living" .)