Related Clues:

• Burrowing mammal
• Person with a code name, maybe
• Intelligence agent
• Unwelcome plant?
• Planted agent
• Underground mammal
• Spy-in-hiding
• Suburban burrower
• Valerie Plame, e.g.
• Espionage expert
• Lawn tunneler
• Mole, e.g. 19. Thumbs-down vote
• Double agent, e.g.
• U-2 pilot, e.g.
• Burrowing critter