A horse moved onto land (6)
I believe the answer is:
ashore
'onto land' is the definition.
(synonyms)
'a horse moved' is the wordplay.
'moved' indicates an anagram.
'horse' with letters rearranged gives 'shore'.
'a'+'shore'='ASHORE'
(Other definitions for ashore that I've seen before include "Off the boat" , "Home for the sailor" , "Going on land from sea" , "Toward land from water" , "Onto land (from the water)" .)