The term 'TROTTER's Kin' is a crossword solution for the word 'PACER', which is a five-letter word. A PACER is a type of horse that is used in harness racing, and is related to the TROTTER breed of horse. Trotters are known for their ability to move at a steady pace, and pacers are bred from trotters to have the same ability. PACER horses are used in harness racing, where they pull a two-wheeled cart with a driver inside.