Support answer further with main point about apostle (12)

I believe the answer is:

propagandist

I'm a little stuck... Click here to teach me more about this clue!

'apostle' is the definition.
(thesaurus)

'support answer further with main point about' is the wordplay.
'support' becomes 'prop' (prop up can mean to support).
'answer further' becomes 'a' (abbreviation eg in Q and A. I am not sure about the 'further' bit.).
'with' becomes 'and'.
'main point' becomes 'gist' (the main point or meaning of something).
'about' means one lot of letters goes inside another.
'and' put inside 'gist' is 'gandist'.
'prop'+'a'+'gandist'='PROPAGANDIST'

Can you help me to learn more?

(Another definition for propagandist that I've seen is " evangelist".)

I've seen this clue in The Telegraph.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.