Related Clues:

• Vital
• Coral reef
• Major
• Pivotal
• One of 88
• F, G, but not H
• Hotelier's handout
• 53-Down is one
• Cryptographer's aid
• He wrote "Defense of Fort M'Henry"
• Speck in the ocean
• Indispensable
• "Defense of Fort M'Henry" author
• Tab, for one
• Map part