The term 'FIXER AT A HORSE RACE' can be summarized as a person who is responsible for ensuring the fairness of a HORSE RACE. The crossword solution for this term is 'VET', which stands for veterinarian. A veterinarian is a professional who is trained to diagnose and treat diseases and injuries in animals, including horses. In the context of a HORSE RACE, a veterinarian would be responsible for ensuring that all horses are healthy and fit to compete, and that no unfair practices are taking place.