Switch posts near ground (9)
I believe the answer is:
transpose
'switch' is the definition.
(I've seen this before)
'posts near ground' is the wordplay.
'ground' indicates an anagram ('grind' the letters into a new form).
'posts'+'near'='postsnear'
'postsnear' is an anagram of 'TRANSPOSE'.
(Other definitions for transpose that I've seen before include "Change position of patroness" , "play in different key" , "Write (music) into different key" , "Cause to change places" , "7 down (anag)" .)