A sect's cilice prepared for cleric (12)
I believe the answer is:
ecclesiastic
'cleric' is the definition.
(synonyms)
'a sect's cilice prepared' is the wordplay.
'prepared' indicates anagramming the letters.
'a'+'sects'+'cilice'='asectscilice'
'asectscilice' with letters rearranged gives 'ECCLESIASTIC'.
'for' acts as a link.
(Other definitions for ecclesiastic that I've seen before include "Cleric" , "Member of clergy; or, relating to church" , "Churchman" , "Religious" , "Relating to clergymen" .)