A wild horse on land (6)
I believe the answer is:
ashore
'on land' is the definition.
(synonyms)
'a wild horse' is the wordplay.
'wild' indicates an anagram.
'horse' anagrammed gives 'shore'.
'a'+'shore'='ASHORE'
(Other definitions for ashore that I've seen before include "On(to) dry land" , "Toward land from water" , "Hoarse being no longer at sea" , "in port?" , "beach" .)