Change back row (9)
I believe the answer is:
rearrange
'change' is the definition.
(I've seen this before)
'back row' is the wordplay.
'back' becomes 'rear' (something's rear is its back).
'row' becomes 'range' (range can mean a row or chain of things).
'rear'+'range'='REARRANGE'
(Other definitions for rearrange that I've seen before include "Organise another way" , "Rear anger (anag.)" , "Move around" , "Make an anagram of" , "Order differently" .)