The term 'TRACK PART' refers to the components of a railroad track. The three solutions are RUT (3 letters), RAIL (4 letters), and CROSSTIE (8 letters). A RUT is a groove or depression in the ground, which is used to guide the wheels of a train. Rails are metal bars that are laid in parallel lines along the track, and provide a surface for the train to travel on. Crossties are wooden beams that are placed between the rails to keep them in place and provide support.