Sect members take brief moment followed by terrible noise (7)
I believe the answer is:
moonies
'sect members' is the definition.
I don't know anything about this answer so I cannot tell whether this works.
'brief moment followed by terrible noise' is the wordplay.
'brief moment' becomes 'mo' (as in 'just a mo'; 'brief' suggests an abbreviation).
'followed by' means one lot of letters go next to another.
'terrible' indicates an anagram.
'noise' with letters rearranged gives 'onies'.
'mo'+'onies'='MOONIES'
'take' is the link.
Can you help me to learn more?
(Another definition for moonies that I've seen is " Unification Church adherents".)