Related Clues:

• Number between due and quattro
• One past due
• Crumble over time
• Certain numero
• Disappear slowly but surely
• Chip away at, as confidence
• Rub away
• Un numero
• Wear away, as popularity
• Wash away
• 'Uno' + 'due'
• Become worn down
• Low numero
• Shorelines do it
• Eat at the bank?