Related Clues:

• It's a sign
• Actor's aid
• Mayday! Mayday!
• Main message?
• Stick in a hall?
• Dashed-off message?
• Cry of distress
• Visible part of an iceberg
• Something helpful
• Brillo competitor
• Mayday letters
• Desperate characters?
• Pool ____
• It replaced CQD
• About 15%, usually