Jacob Clear began kayaking in 2006 through surf lifesaving which he started at the age of five as a nipper. Clear won the U/19 single ski event at the 2003 Australian Surf Lifesaving Championships and won bronze in the open event the following year. In 2005 Clear was selected as part of a kayaking talent identification program. Switching his focus to sprint paddling, Clear won the U/23 K1 1000m and K1 500m in his second year in the sport at the 2007 National Championships. He then made his debut on the Australian team in 2007 and competed at the 2008 Olympic Games. Clear kayaked in the K2 500m in Beijing with Clint Robinson and placed 13th.
At the 2011 World Championships in Hungary, Clear was part of the men's K4 1000m crew that won silver. He also won a silver and bronze medal at the 2011 World Cups in the Czech Republic and Germany.
He returned to Olympic competition at the London 2012 Games having qualified as a part of the K4 1000m crew with Murray Stewart, David Smith and Tate Smith. Finishing 3rd in their heat, the team looked impressive as they topped their semi-final and headed into the Olympic final full of confidence. Leading by under a tenth of a second at the halfway mark, the Australians beat home the Hungarians by 0.61 seconds to win the gold medal. The crew was the only Australians to win gold at Eton Dorney at the London 2012 Games.