England's Graeme Storm carded a 69 to finish one shot off the pace at 8-under-par 208. David Howell, a member of the winning European team at the Ryder Cup at Oakland Hills, shot a 67 to join Gregory Havret, Bobby Lincoln and Neil Cheetham at 6-under-par 210.
Clark was four shots behind Moore to start the day at Durban Country Club and was steady over the tough opening holes. He coasted at even-par until he reached the par-4 third, a hole Clark had bogeyed and double bogeyed in rounds one and two, respectively.
This time around was different for Clark, however, and the 29-year-old birdied the hole that had troubled him in the early rounds. That birdied kickstarted Clark's round and he added birdies on the next two holes to move to 8 under.
Clark then ran off another string of pars, all the while residing just behind the leaders. He closed his round with a birdie at the par-4 18th and waited as his challengers faltered on the closing holes to force the logjam atop the leaderboard.
'The last time I was in this position I shot 7 under to win so I am certainly going to be very confident tomorrow,' said Clark, recalling the 2002 tournament. 'In the final round you can't be too conservative because you have to figure that someone is going to have a good round.'
Moore, who held a two-shot lead over van der Walt and Buhrmann heading into the weekend, picked up a quick birdie at the third to maintain his advantage. Moore found trouble with a bogey at the seventh, however, and dropped another shot with a bogey at the 11th to fall back to minus-8.
The 28-year-old countered with a birdie at the 12th and join Buhrmann at 10 under with a birdie at the par-5 14th. Moore then gave that shot back with a bogey at the 16th for a round of 72.
Buhrmann took the lead with a birdie at the 13th, but followed Moore with a bogey of his own at the 16th for his share of first.
'This week I have played very conservatively and it has paid off,' said Buhrmann, who shot a 70. 'It is the first time I have tried to play like that because I am an aggressive player and that has cost me in the past but I have really controlled myself this week and maybe that is why I am still here.'
Van der Walt had four birdies and four bogeys on his round before he reached the short par-4 18th. The 30-year-old's drive was a good one and he was left with a 10 foot putt for an eagle, his second of the week at the last and third overall, and a round of 70.
Charl Schwartzel, who won the dunhill championship in December, carded a 71 to share 10th place with Bruce Vaughan and Louis Oosthuizen at 5-under-par 211. Two-time defending champion Trevor Immelman followed at 4-under-par 210 along with Ian Garbutt, Jaco Van Zyl, Lee Slattery and Garry Houston.
Darren Clarke, who survived the cut on the number Friday, fired a 67 to finish six shots back in a group at 3-under-par 213.