Related Clues:

• Mole, maybe
• Bug someone, e.g.
• Catch a glimpse of
• Stratego piece
• Maxwell Smart, for one
• Watch covertly
• Snoop (on)
• Microfilmer, maybe
• Sneak a peek
• Double agent
• CIA operative
• Be a snoop
• Black or white Mad character
• "I ---"
• 007, for one