Related Clues:

• Tough thing to crack
• Pecan, for one
• "Headcase" is regularly used in insults
• Fruitcake ingredient
• Energy bar bit
• Source of a common allergy
• Beer __
• Filbert or cashew
• Baklava morsel
• Brazil ___
• Hard edible seed
• Black Flag "Loose ___"
• Crazy frontman
• '94 Tesla album "Bust a ___"
• XTC "Fruit ___"