Moved a mile to make address better (10)
I believe the answer is:
ameliorate
'better' is the definition.
(to ameliorate is to make better)
'moved a mile to make address' is the wordplay.
'moved' is an anagram indicator.
'to make address' becomes 'orate' (to orate is to give a speech or address).
'a'+'mile'='amile'
'amile' anagrammed gives 'ameli'.
'ameli'+'orate'='AMELIORATE'
(Other definitions for ameliorate that I've seen before include "seen to improve" , "Make (a bad thing) better" , "Become better" , "Make (something) better" .)