Create pure chaos but improve (10)
I believe the answer is:
recuperate
'improve' is the definition.
(I know that recuperate is a kind of improve)
'create pure chaos' is the wordplay.
'chaos' indicates an anagram.
'create'+'pure'='createpure'
'createpure' with letters rearranged gives 'RECUPERATE'.
'but' is the link.
(Other definitions for recuperate that I've seen before include "Rally, recover" , "Convalesce" , "Recover from an illness" , "Get better" .)