The Northern Irishman is tied with Austrian Uli Weinhandl, who Monday-qualified for the event. Both players competed on the Lost City course in Round 1. Mark Foster, who won last weeks Dunhill Championship on the European Tour, shot 66 to take solo third place.
American Bruce Vaughn had the lowest score on the Gary Player course, a 4-under 68. The players will alternate between the two courses over the first two days, before settling on the Gary Player venue for the weekend.
Nick Price will be looking forward to a return to the Gary Player course, where he won three Nedbank Challenge events. He has also won this tournament twice, in 1997 and 98.
Price opened in 3-under 69 on the Lost City course, along with Englands Justin Rose.
Unlike many, Clarke was making his competitive debut in 2003 on Thursday. He shot 29 on his back nine, and put himself in good position to capture his second Dimension Data title in the last three years. He edged out Retief Goosen in 2001.
Great first week out, said Clarke, who has had to move out of his new home in England while it is being refurbished.
We have builders trying to fix the heating, so all the builders have moved in. Were staying down here in Africa for another five days after this tournament.
In addition to his new surroundings, Clarke is adjusting well to his new driver, new ball, new irons and new caddie. Clarke is using Paul McGinleys caddie since his regular looper, Billy Foster, is injured.
Clarke started the day on the 10th, but shot up the leaderboard on the front side. He made an eagle and four consecutive birdies on holes 4-8.
Weinhandl doesnt have Clarkes reputation, but he was able to match the Ryder Cupper for at least one day. In fact, the Austrian is lucky to be playing golf at all after suffering a serious motorcycle accident two years ago.
He spent 10 days in the hospital and seven weeks on crutches. It wasnt until November that he had the last few metal pins and screws removed from his body.
I only started play at the beginning of January. My hip is still a little sore, said Weinhandl, who plays mostly on the European Challenge Tour.