Despotic writer appears before Italian heretic (13)
I believe the answer is:
authoritarian
'despotic' is the definition.
(synonyms)
'writer appears before italian heretic' is the wordplay.
'writer' becomes 'author' (synonyms).
'appears before' says to put letters next to each other.
'italian' becomes 'it' (abbreviation for Italian).
'heretic' becomes 'arian' (Arianism is a form of heresy).
'author'+'it'+'arian'='AUTHORITARIAN'
(Other definitions for authoritarian that I've seen before include "Dictatorial" , "despot" , "Enforcing strict rules" , "Enforcing strict obedience" , "Oppressively strict" .)