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