English archdeacon of a smooth nature (4)
I believe the answer is:
even
'of a smooth nature' is the definition.
(even can mean smooth)
'english archdeacon' is the wordplay.
'english' becomes 'e' (abbreviation).
'archdeacon' becomes 'ven' (abbreviation for The Venerable).
'e'+'ven'='EVEN'
(Other definitions for even that I've seen before include "Nearly" , "That's not odd" , "Quits - flat" , "Tied" , "Constant" .)