Confront Simon, awful heretic (13)
I believe the answer is:
nonconformist
'heretic' is the definition.
(thesaurus)
'confront simon awful' is the wordplay.
'awful' indicates anagramming the letters.
'confront'+'simon'='confrontsimon'
'confrontsimon' is an anagram of 'NONCONFORMIST'.
(Other definitions for nonconformist that I've seen before include "One opposed to the establishment" , "Confirm son? Not! (anag)" , "Breaking with established ideas" , "One at odds with the Establishment" , "An original" .)