Agree on the essential modern social orders (6)

I believe the answer is:

decide

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

'agree' is the definition.
Although both the answer and definition are verbs in their base form, I cannot understand how they can define each other.

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for decide that I've seen before include "Conclude" , "Reach a judgment" , "Settle conclusively" , "Resolve; give judgement" , "Come to a resolution" .)

I've seen this clue in The Irish 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.