Italicus is in Paris defending Thailand's religious society (7)
I believe the answer is:
jesuits
'italicus is in paris defending thailand's religious society' is the definition.
I can't judge whether this definition defines the answer.
'italicus is in paris defending thailand's' is the wordplay.
'italicus' becomes 'I' (where the crossword setter is 'Italicus').
'is in' indicates putting letters inside.
'paris' becomes 'jesus' (I can't justify this - if you can you should believe this answer much more).
'defending' is an insertion indicator (inserted letters are defended).
'thailand' becomes 'T' (abbreviation on car registration plates).
'jesus' enclosing 't' is 'jesuts'.
'i' inserted into 'jesuts' is 'JESUITS'.
Can you help me to learn more?
(Another definition for jesuits that I've seen is " Priests".)