Only aim to change maintenance (7)
I believe the answer is:
alimony
'maintenance' is the definition.
(synonyms)
'only aim to change' is the wordplay.
'to change' indicates an anagram.
'only'+'aim'='onlyaim'
'onlyaim' with letters rearranged gives 'ALIMONY'.
(Other definitions for alimony that I've seen before include "A cost of divorce?" , "Payment to divorcee" , "financial support separately provided" , "Allowance paid to spouse after divorce" , "Allowance payable to divorced wife" .)