Related Clues:

• Scoun-drel
• Insect
• 'You dirty --!'
• Stool pigeon
• One who sings
• Wharf pest
• Sewer resident
• Common test subject
• Muppet Rizzo, e.g.
• Plague carrier
• Dirty dog
• Nocturnal rodent
• Untrustworthy one
• Contemptible fellow
• Lab maze runner