The brotherhood expresses a reservation (5)

I believe the answer is:

order

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

'the brotherhood' is the definition.
(I've seen this in another clue)

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for order that I've seen before include "Ruling" , "Regular or proper arrangement" , "Direct or requisition" , "Command, injunction" , "demanding firm discipline" .)

I've seen this clue in The Globe and Mail.

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.