In the final round, he gained momentum by making birdies from holes 10-12. His bogeys at the second and 15th holes were negated by six birdies overall.
"It's nice to come somewhere knowing that I had to play well and then actually do it," Clarke said after winning for the 12th time on the European Tour.
His latest victory came while his two sons saw him win in person for the first time.
His 72-hole total, 16-under 264, was one stroke shy of the tournament record.
Paul McGinley (64) finished second at 12-under 268.
Neither Clarke nor McGinley is qualified for the European Ryder Cup team.
Lee Slattery (65) and Marc Warren (68) shared third place at 9-under 271.
Henrik Stenson, the world's sixth-ranked player, birdied the first three holes to take the early lead, but finished fourth at 11-under 269.