At the 2019 World Para Athletics Championships in Dubai, Clifford set a world record time of 3:47.78 in winning the gold medal in the Men's 1500m T13. Clifford with his two guides Tim Logan and Philo Saunders won the Men's 5000m T13. Clifford stated he needs guides for the 5000m due to his deteriorating eyesight making the event dangerous for him.