Either side of a Mad magazine battle (3)

I believe the answer is:

spy

(Other definitions for spy that I've seen before include "Mole, agent" , "Undercover agent" , "Enemy agent" , "Catch sight of" , "Spot" .)

I've seen this clue in the Universal.

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.