That man is enthralled by right-wing notion (6)
I believe the answer is:
theory
'notion' is the definition.
(thesaurus)
'that man is enthralled by right-wing' is the wordplay.
'that man' becomes 'he'.
'is enthralled by' is an insertion indicator ('enthral' can mean 'capture').
'right-wing' becomes 'tory'.
'he' going inside 'tory' is 'THEORY'.
(Other definitions for theory that I've seen before include "abstract reasoning" , "General principle which explains some aspect of the world" , "Conjectural view" , "Unproven explanation" , "Set of ideas formed from reasoning" .)