Clark qualified for the 2005 PDC World Darts Championship, going through the first round against Japan's Yasuhiko Matsunaga, but lost in round two to Chris Mason. In the 2006 PDC World Darts Championship, he defeated Steve Maish in the first round, but narrowly lost in the second round to Peter Manley. After failing to qualify for the 2007 World Championship, he won a place in the 2008 PDC World Darts Championship as one of the highest ranked players in the 2007 PDC Pro Tour. He defeated 1988 World Champion Bob Anderson in the first round, but lost in the second round to then-current World Champion Raymond van Barneveld.