Satan a bit silly admits quiet Protestant (10)
I believe the answer is:
anabaptist
'protestant' is the definition.
(Anabaptist is an example)
'satan a bit silly admits quiet' is the wordplay.
'silly' indicates anagramming the letters.
'admits' indicates putting letters inside (to admit is to allow in).
'quiet' becomes 'p' (music symbol for 'piano', ie soft or quiet).
'satan'+'a'+'bit'='satanabit'
'satanabit' is an anagram of 'anabatist'.
'anabatist' going around 'p' is 'ANABAPTIST'.
(Another definition for anabaptist that I've seen is " Protestant sect member".)