Military alliance headquartered in Brussels (4)

I believe the answer is:

nato

(Other definitions for nato that I've seen before include "Military/political alliance" , "US/Europe alliance" , "Military organization" , "Military alliance, formed 1949" , "International organisation for collective security" .)

I've seen this clue in The Guardian.

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.