Related Clues:

• Give an alert (to)
• Like a sentry
• Shoot off a flare, e.g.
• Notify of peril
• Alert and suspicious
• Serve notice
• Premonish
• Vigilant against attack
• Shout "Fore!" to
• Inform of danger
• Try to save, maybe
• Show a yellow card, e.g.
• Issue a caveat to
• Say "Be careful" to
• Alert of danger