Related Clues:
- Colorful warning, often
- Wide awake to a siren call
- Danger signal, e.g
- Keenly attentive
- Sharp tip off
- All-points bulletin, e.g
- Like prairie dogs, notably
- Offer a heads-up
- Keeping one's eyes peeled at crumbling alter
- Watch chain not originally belonging on watch?
- Like a good lookout
- Wake-up call, say
- Not easy to fool
- Fit for guard duty
- Warning - answer the French resistance on time!