Clergyman rejected nonsense by idiot (6)
I believe the answer is:
pastor
'clergyman' is the definition.
(I know that pastor is a type of clergyman)
'rejected nonsense by idiot' is the wordplay.
'rejected' shows that the letters should be reversed in order.
'nonsense' becomes 'rot' (rot can mean nonsense or rubbish).
'by' is a charade indicator (letters next to each other).
'idiot' becomes 'sap' (sap can mean a foolish or gullible person).
'rot'+'sap'='rotsap'
'rotsap' in reverse letter order is 'PASTOR'.
(Other definitions for pastor that I've seen before include "who may provide a service" , "Member of the clergy" , "Christian minister" , "To spar with clergyman" , "Minister; shepherd" .)