Is able to get ahead as a cleric (5)
I believe the answer is:
canon
'a cleric' is the definition.
(I've seen this before)
'is able to get ahead' is the wordplay.
'is able to' becomes 'can' (I've seen this before).
'get' says to put letters next to each other.
'ahead' becomes 'on' ('on' can be a synonym of 'ahead').
'can'+'on'='CANON'
'as' is the link.
(Other definitions for canon that I've seen before include "senior cleric" , "Collection of writing" , "Member of a cathedral chapter" , "Body of generally established principles for a given context" , "Principle - member of cathedral staff" .)