Shady religious school of opinion keeping us quiet (7)
I believe the answer is:
suspect
'shady' is the definition.
(I know that shady can be written as suspect)
'opinion keeping us quiet' is the wordplay.
'opinion' becomes 'sect' (I am not sure about this - if you are sure you should believe this answer much more).
'keeping' means one lot of letters goes inside another (some letters kept inside).
'quiet' becomes 'p' (music symbol for 'piano', ie soft or quiet).
'us'+'p'='usp'
'sect' going around 'usp' is 'SUSPECT'.
'religious school of' acts as a link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for suspect that I've seen before include "man distrusted?" , "Have misgivings about" , "Doubt - man held by police" , "Imagine to be guilty" , "Believe (someone) guilty" .)