High priest, maybe, that keeps rejoicers oddly suppressed (8)
I believe the answer is:
theocrat
I'm afraid I can't explain this answer.
Can you help me to learn more?
(Other definitions for theocrat that I've seen before include "One involved in government by religious leaders" , "Deified ruler" , "Roman emperor, for example" , "priest-in-charge" , "Moses, for example" .)