Clarke, a Ryder Cup regular, moved to 9-under 207 for a one-shot lead over second-round co-leader Robert-Jan Derksen (69) of the Netherlands. Englands Robert Dinwiddie finished strongly to record the best round of the day, a 6-under 66, to move a stroke behind Derksen.
Chinas Zhang Lianwei, who was tied with Derksen after the second round, dropped back after a 4-over 76, but compatriot 18-year-old amateur Hu Mu maintained his unlikely challenge, sinking an eagle on the 17th to finish with a 1-under 71, six strokes off the lead.
Clarke had five birdies and no bogeys, relishing the challenge of taming a difficult Tomson Shanghai Pudong course in the jointly sanctioned European Tour and Asian Tour event.
I was in contention a few times at the start of the season but it has been a while since I led and I am really looking forward to it and I just hope I can continue doing what I have been, Clarke said. It is a really good golf course, a stern test. You have to control you ball flight and shape of your shots to get it close and it is the type of course I enjoy.
Derksen also had five birdies, plus two bogeys, while preserving his 69 by saving par on the par-3 14th despite finding water off the tee.
I felt that it was important to keep myself in the last group for tomorrow, and Ive achieved that, so that I can see what the others are doing, Derksen said.
Dinwiddie, in his rookie season on the full European Tour after graduating from the Challenge Tour, birdied six of the final 10 holes to position himself for a chance at his first title.
I putted very, very well for those last ten holes and pretty much one-putted every green, Dinwiddie said.
Lin Wentang of Taiwan was the best placed of the Asian players, in fourth, four shots off Clarke. He moved to the top of the leaderboard by going through the front nine in four-under 32, before an adventurous back nine where he double-bogeyed the 10th, bogeyed again on 13, clawed back with birdies on 16 and 17 before saving par on the last with a 15-foot putt.
The worlds No. 13 Henrik Stenson had an even par 72 to be nine shots off the lead.