Hookup for an undercover agent

WIRE

Think of what a spy might wear discreetly to transmit conversations—it’s not a device you’d see, but it’s essential for covert communication.

An undercover agent often wears a "wire," which is a hidden listening device to secretly record conversations. The clue plays on the double meaning of "hookup"—both as a connection (like a wire) and as slang for a romantic encounter, though here it’s purely about spy gear. The answer is straightforward once you think of espionage tools rather than dating.