ONE AND ONLY ONE

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Across
  1. 2. a one-piece leotard and tights combination
  2. 3. having only one cell
  3. 5. an instance of saying the same words or sounds at the same time; a group that sounds like one
  4. 6. a one-wheeled vehicle on which the rider sits and pedals
  5. 7. one sided
Down
  1. 1. moving in only one direction
  2. 3. one group
  3. 4. one of a kind; unusual or rare
  4. 5. a horse-like fabled animal that has one horn growing out of the middle of its forehead
  5. 7. to join together into one group