Related Clues:

• 53-Down is one
• Word with organ or sign
• Cryptographer's aid
• He wrote "Defense of Fort M'Henry"
• Speck in the ocean
• Indispensable
• Like some organs
• "Defense of Fort M'Henry" author
• Of utmost importance
• Tab, for one
• Map part
• Free-throw area
• Anthem author
• CTRL, e.g.
• Integral