Restore a Blairite? The changes! (12)
I believe the answer is:
rehabilitate
'restore' is the definition.
(rehabilitating is a kind of restoring)
'a blairite? the changes' is the wordplay.
'changes' is an anagram indicator.
'a'+'blairite'+'the'='ablairitethe'
'ablairitethe' is an anagram of 'REHABILITATE'.
(Other definitions for rehabilitate that I've seen before include "Restore the reputation of (someone)" , "Restore to health" , "Restore after adversity" , "Restore to favour, position" , "Get back to normal" .)