One minute before noon, prayer leader appears (4)
I believe the answer is:
'prayer leader appears' is the definition.
I can't judge whether this definition defines the answer.
'one minute before noon' is the wordplay.
'one' becomes 'i' (Roman numeral).
'minute' becomes 'm' (abbreviation).
'before noon' becomes 'AM' (as in AM on a clock).
Can you help me to learn more?
(Other definitions for imam that I've seen before include "Ma, I'm off to find religious Muslim" , "Maim (anag)" , "Muslim prayer leader" , "Islamic minister" , "Islamic prayer leader" .)