Related Clues:

• Mentally responsive
• Let it all out
• It may be red
• Qui vive
• All ears
• Wide-awake
• Ready to jump, perhaps
• On guard
• Wary
• Whistle, maybe
• Be lachrymose
• 1951 #1 hit for Johnny Ray
• At the ready
• Go "waaaah"
• Exclamation