Ascetic pair in a cult novel (11)
I believe the answer is:
puritanical
'ascetic' is the definition.
(thesaurus)
'pair in a cult novel' is the wordplay.
'novel' indicates an anagram.
'pair'+'in'+'a'+'cult'='pairinacult'
'pairinacult' is an anagram of 'PURITANICAL'.
(Other definitions for puritanical that I've seen before include "Strict-minded" , "likely to curtail pleasure" , "Strictly moral in conduct" , "Morally very strict" , "Very strict, censorious" .)