Muezzin's faith (5)
I believe the answer is:
islam
'muezzin's faith' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for islam that I've seen before include "Religion of the Koran" , "Mails to Muslim religion" , "Belief" , "Major world religion" , "Faith with five pillars" .)