Church member a monarchic lot abused (5,8)
I believe the answer is:
roman catholic
'church member' is the definition.
(I've seen this before)
'a monarchic lot abused' is the wordplay.
'abused' indicates anagramming the letters.
'a'+'monarchic'+'lot'='amonarchiclot'
'amonarchiclot' with letters rearranged gives 'ROMAN CATHOLIC'.
(Other definitions for roman catholic that I've seen before include "RC in full" , "Its head is the Pope" , "Church member" , "Religious believer" .)