Former arrangement to change for the better (6)
I believe the answer is:
reform
'change for the better' is the definition.
(synonyms)
'former arrangement' is the wordplay.
'arrangement' indicates an anagram.
'former' anagrammed gives 'REFORM'.
'to' is the link.
(Other definitions for reform that I've seen before include "Change one's ways (for the better?)" , "Correct(ion of) abuses" , "Mend one's ways" , "Show improvement" , "Go straight" .)