Related Clues:

• 15%-20%, usually
• Pen end
• Help line?
• Part of a pointer
• It's left on the table
• Subject of an anonymous call, maybe
• Service bonus
• Bit of help
• Part of an iceberg that's visible
• Helpful suggestion
• Wait for it
• Leave cash
• You leave it behind in a restaurant
• Iceberg feature, figuratively
• Redcap's reward