Related Clues:

• Courage
• Backbone
• Wear down little by little
• Indomitable spirit
• Bite like a beaver
• Chew on celery, e.g.
• Nibble away
• Determination
• Sandpaper coating
• Spunk
• Prey on one's mind
• Emulate a beaver
• Wear down
• Sandpaper surface
• Work like a beaver