Related Clues

• With ears pricked
• On the qui vive
• Tip off
• Red ___
• Tornado siren, e.g.
• Wide-eyed
• Ready
• Heads up
• Heads-up
• Argus-eyed
• Open-eyed
• Red flag
• Like a good guard
• Ready for anything
• Notify of danger
• On the ball
• "Heads up!," e.g.
• Yellow ___
• With it
• On one's toes