Cleric entering cathedral city in a calm manner (6)
I believe the answer is:
evenly
'in a calm manner' is the definition.
(I've seen this in another clue)
'cleric entering cathedral city' is the wordplay.
'cleric' becomes 'ven' (abbreviation for The Venerable).
'entering' is an insertion indicator.
'cathedral city' becomes 'Ely' (English city with a cathedral).
'ven' placed into 'ely' is 'EVENLY'.
(Other definitions for evenly that I've seen before include "on an equal footing" , "not getting ruffled" , "at regular intervals" , "Equally or smoothly" , "avoiding hiccups?" .)