Related Clues:

• See 114-Down
• Notice
• On the qui vive
• Danger signal
• Siren
• Red flag
• See 42-Down
• Ready for anything
• No longer asleep
• Active
• '___ and Sing!' (1935 play by 65-Across)
• Notify of danger
• On the ball
• Like a good guard
• 'Heads up!,' e.g.