Crazily invest more to secure MP's changes for the better (12)
I believe the answer is:
improvements
'changes for the better' is the definition.
(I've seen this before)
'crazily invest more to secure mp's' is the wordplay.
'crazily' indicates an anagram.
'to secure' is an insertion indicator.
'invest'+'more'='investmore'
'investmore' anagrammed gives 'irovements'.
'irovements' placed around 'mp' is 'IMPROVEMENTS'.
(Other definitions for improvements that I've seen before include "Changes for the better" , "Reforms" , "advances" , "better progress" .)