The native of Northern Ireland concluded his bogey-less round with a birdie at the 18th and final hole. His three-round total is 9-under 207.
Clarke began the day one stroke behind overnight co-leaders Dirksen, of the Netherlands, and China's Zhang Lian-Wei.
This is the five-time Ryder Cup player's first 54-hole lead on the European Tour since 2003.
"I played really well today," Clarke said. "I was very pleased with the way I hit the ball. For the most part I had the ball under control for the shots I was trying to hit (and) I am really looking forward to (Sunday)."
Dirksen (69) is alone in second place at 8-under 208.
England's Robert Dinwiddie (66) is third at 7-under 209, while Zhang's 4-over 76 left him tied for 15th place at 1-under 215.