Related Clues:

• Put on guard
• Red state?
• Like a worthy watchdog
• Having heightened senses
• APB, for one
• A serious one may be red
• Storm warning
• Emulate Paul Revere
• "Fore!" for one
• Give a heads-up to
• Readiness condition
• Yellow flag
• Fully conscious
• Clear-witted
• Full of NoDoz