Necessarily involves a silent reformation (7)
I believe the answer is:
entails
'necessarily involves' is the definition.
(I've seen this in another clue)
'a silent reformation' is the wordplay.
'reformation' indicates an anagram.
'a'+'silent'='asilent'
'asilent' anagrammed gives 'ENTAILS'.
(Other definitions for entails that I've seen before include "Has as a direct consequence" , "Necessitates" , "Has as a logical consequence" , "Involves, makes necessary" , "limits of will" .)