Piece of wampum is a traditional form of currency used by Native American tribes. It is made from beads of shells, usually white and purple, which are strung together into belts or other forms. The term 'piece of wampum' refers to a single BEAD or a small group of beads. The crossword solution for this term is BEAD, which is an appropriate answer as it accurately describes the material used to make wampum.