Related Clues:

• Dennis of comics, for one
• Peril
• Indication of doom
• Loose cannon
• Words from a blackmailer
• Time bomb, say
• Sand trap, for one
• Ultimatum, for example
• Rattle a saber at
• Links challenge
• Shark, e.g.
• Thug's message
• 'Dennis the --'
• Black ice, e.g.
• One waving a loaded gun, e.g.