Reformist’s new blazer (9)
I believe the answer is:
firestorm
'blazer' is the definition.
(something which blazes)
'reformist's new' is the wordplay.
'new' indicates anagramming the letters.
'reformist' with letters rearranged gives 'FIRESTORM'.
(Other definitions for firestorm that I've seen before include "devastating thing" , "big blazer" , "blaze" .)