M's top agent (4)

I believe the answer is:

bond

(Other definitions for bond that I've seen before include "Written promise" , "Fastening; secret agent" , "secure?" , "Join, double 'O' seven" , "Fellow feeling" .)

I've seen this clue in the King Feature Syndicate and the Wall Street Journal.

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.