Related Clues:

• Government agent
• Watch furtively
• Mole, for example
• View slyly
• Mole, perhaps
• Cover girl, e.g.?
• Ingrid in "Notorious," e.g.
• Unwelcome plant
• One undercover
• With 5-Down, snooping aid
• Thriller hero, often
• 'Alias' type
• One with a code name, perhaps
• Nathan Hale, notably
• Bug planter