Changing mate? It is for apes (8)
I believe the answer is:
imitates
'apes' is the definition.
('imitate' can be a synonym of 'ape')
'changing mate? it is' is the wordplay.
'changing' is an anagram indicator.
'mate'+'it'+'is'='mateitis'
'mateitis' is an anagram of 'IMITATES'.
'for' is the link.
(Other definitions for imitates that I've seen before include "Apes" , "Copies, takes off" , "Mimics or simulates" , "Copies, simulates" .)