Reinforce mysterious brotherhood (9)

I believe the answer is:

confrerie

'brotherhood' is the definition.
(thesaurus)

'reinforce mysterious' is the wordplay.
'mysterious' is an anagram indicator.
'reinforce' is an anagram of 'CONFRERIE'.

I've seen this clue in The Times.

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.