Go off high ground to the west (3)
I believe the answer is:
rot
'go off' is the definition.
(I've seen this before)
'high ground to the west' is the wordplay.
'high ground' becomes 'tor'.
'to the west' says the letters should be written backwards (letters written right to left or \'east to west\').
'tor' in reverse letter order is 'ROT'.
(Other definitions for rot that I've seen before include "Break down, waste away" , "Deteriorate" , "Decay, moulder" , "bunk" , "Corruption" .)