Clark had a two-round total of 7-under 137, a stroke ahead of Australians Anthony Summers, who shot a 68, and Michael Sim, who had a 66.
Seven players were one stroke further back at 5 under, including former winner Robert Allenby, who picked up five shots on the back nine for a second-round 66. Another in that group was Australian Aaron Townsend, who had a second-round 64 after completing his first-round 75 on Friday morning.
John Daly shot a 73 after an opening 76 and missed the cut at 5 over. Hell remain Down Under to play in next weeks Australian PGA at Coolum in Queensland state.
I had a couple of eagle opportunities and hit horrible putts, and three-putted one of them, Daly said.
The field in the joint European and Australasian PGA Tour event took full advantage of calm, quiet conditions on Friday on a course softened by overnight rain. On Thursday, a storm and hail caused a three-hour suspension in play, forcing 39 golfers to complete their rounds on Friday morning.
Clark said he failed to take advantage of the easier conditions.
I had a lot more birdie chances and with the greens being softer it was easier to get it closer, and I just didnt make anything, Clark said. I made one putt of about eight feet for birdie on No. 1 which was my back nine, and that was it all day.
Summers, who finished 10th in last years Masters, just returned from Europe, where he missed qualifying for his European Tour card by one stroke.
When I hit a bad one, I got away with it, and when I hit the good ones I made the most of them, so it was a good day, said Summers. I get to play the weekend, thats a great bonus.
Townsend completed the final five holes of his first round on Friday morning, and bogeyed four of them. But after a short break for some tea and toast, he had nine birdies and one bogey in his second round to equal the Huntingdale course record.
Ive sort of got a feel for it at the moment, Townsend said.