Clement's family moved to the United States in 1998, where he became a successful high school athlete at La Porte, Texas winning both 110 and 400 metres hurdles at the USATF Youth Athletics Championships.
Clement became a U.S. citizen in June 2004. In July 2004 he won the gold medal in the 400 metres hurdles in an IAAF World Junior Championships record time of 48.51 seconds in Grosseto Italy. Clement also ran a leg for the US 4x400m relay team and set a world junior record of 3:01.09. He also won the National Collegiate Athletic Association championships in the 400mH.
On March 12 2005, representing the University of Florida, he broke the indoor world record for the 400m sprint at the NCAA indoor championships in Fayetteville, Arkansas with a time of 44.57 seconds. His split at 200m was 21.08 seconds. The record was held for ten years previously by Michael Johnson at 44.63 seconds. Afterwards Clement anchored Florida’s 4x400 indoor meter relay to a collegiate record of 3:03.51.
Clement set a personal best and 2005 world leading performance in the 400m hurdles with a 47.24 seconds; winning the 2005 US outdoor track and field title at Carson California. This was the fastest time posted for the 400m hurdles in 7 years. Clement faded during the world outdoor championships in Helsinki Finland and did not win a medal, finishing fourth.
Clement qualified in the 400m hurdles for the 2008 Summer Olympics on June 29, 2008 at the Olympic Trials in Eugene, Oregon. Clement, along with the other two American qualifiers, advanced to the finals of 400m hurdles, held on August 18, 2008. Clement was part of a medal-sweep for the United States, winning silver in the 400 meter hurdles.