Related Clues:

• Warning bell
• The ultimate motivator
• Eye opener, of a sort
• Chili-hotness measure
• Perturbation
• Clock partner
• 'An instructor of great sagacity': Emerson
• Snooze, for one
• It might scream after being tripped
• Eyeopener?
• Warning signal
• Uneasy feeling
• Firebox feature
• '___ not!'
• Trepidation