Related Clues:

• "Fore!" for one
• Give a heads-up to
• Readiness condition
• Yellow flag
• Fully conscious
• Clear-witted
• Full of NoDoz
• Not dozing
• Fully attentive
• Like good watchmen
• Fully awake
• Bright-eyed
• Give a heads-up
• Type of post-caffeine state
• Percipient