Shrewd narcs trick churchman (10)
I believe the answer is:
archbishop
'churchman' is the definition.
(I have seen 'Senior churchman ' mean 'archbishop' so perhaps 'churchman' could also mean 'archbishop')
'shrewd narcs trick' is the wordplay.
'shrewd' becomes 'arch' (I've seen this before).
'narcs trick' becomes 'bishop' (I can't justify this - if you can you should give a lot more credence to this answer).
'arch'+'bishop'='ARCHBISHOP'
Can you help me to learn more?
(Other definitions for archbishop that I've seen before include "primate" , "High church rank" , "ecclesiastical dignitary?" , "Chief cleric" , "Senior churchman" .)