Related Clues:

• 53-Down is one
• Word with organ or sign
• Cryptographer's aid
• Disparaging
• He wrote "Defense of Fort M'Henry"
• Speck in the ocean
• Indispensable
• Like some organs
• Not wishy-washy
• Must-have
• "Defense of Fort M'Henry" author
• Of utmost importance
• Dire
• Tab, for one
• Map part