At the start of 2008 he won the 60 m sprint at the Tyson Invitational, but had a poor performance at the 2008 IAAF World Indoor Championships, being eliminated in the heats after a slow start. He competed in only two competitions over 100 m that year: he was a semi-finalist at the Jamaican National Championships and was seventh in the 100 m at the 2008 Central American and Caribbean Championships in Athletics. Driven on by the success of Jamaica at the 2008 Summer Olympics, he competed extensively in the 2009 outdoor season. He was fifth at the Jamaican Championships and took the 100 m silver medal at the 2009 Central American and Caribbean Championships in Athletics with a significant personal best of 10.08 seconds. He also led off the Jamaican relay team which finished as runners-up. He was selected as a first heat relay runner at the 2009 World Championships in Athletics and received a gold medal as the Jamaican quartet went on to win the title. He competed at a number of smaller meets in the European circuit before going on to set a personal best time of 9.99 seconds at the Weltklasse Zürich in August, becoming the 70th man to have broken the 10-second barrier with an official, legal time. Following this he set a meeting record at Rovereto, Italy, recording 10.11 seconds into a headwind to beat Asafa Powell's previous meet best.
Commonwealth champion
In the 2010 indoor season he won at the BW-Bank Meeting, Sparkassen Cup and Erdgas Athletics Meeting. He was chosen for the third time running to run for Jamaica at the 2010 IAAF World Indoor Championships, but was surprisingly eliminated in the heats against lesser opposition. He ran two sub-10-second times at the Doha Athletic Grand Prix, albeit wind-assisted and was a regular competitor on the 2010 IAAF Diamond League circuit. He came fourth at the Jamaican Championships then went on to win a 100 m bronze medal and relay silver medal at the 2010 Central American and Caribbean Games. With the top Jamaican sprinters opting out of the 2010 Commonwealth Games, Clarke was selected to represent his country in the 100 m. He had a fast start in the final and held his lead to win the gold medal, succeeding Asafa Powell as the Commonwealth champion for the event. However, the lack of top athletes was evident from his 10.12-second winning time – the slowest to win the title since Don Quarrie in 1974. He also won a silver medal with the Jamaican relay team. The year after he led off a Jamaican quartet to win the relay gold medal at the 2011 Central American and Caribbean Championships in Athletics and achieved his season's best of 10.01 seconds to win the individual 100 m title at the 2011 Pan American Games. At the 2012 Birmingham Indoor Grand Prix he caused an upset by defeating both Asafa Powell and Nesta Carter over 60 m as he ran a Jamaican record time of 6.47 seconds to win the race.