Related Clues:

• Wide-awake
• Ready to jump, perhaps
• On guard
• Actress Stevens
• Wary
• Whistle, maybe
• Brando's wail in 'A Streetcar Named Desire'
• At the ready
• Far from sleepy
• Bright-eyed and bushy-tailed
• Advance warning
• 'Streetcar' name
• Watching
• Quick on the uptake
• Attentive