Related Clues:

• Look through a keyhole
• Peeper
• Good looker?
• Marilyn Monroe facial feature
• Underground type
• Look in (on)
• Le Carré staple
• Watch secretly
• Finder of secrets
• Mole, maybe
• Unwelcome rooter
• Bug someone, e.g.
• Security concern
• Suburban pest
• Undercover operator