Welshman Jamie Donaldson, trying for his first win in 255 European Tour events at the Irish Open, went two in front of the field with a five-foot birdie putt at the 12th.
However, Dubai Desert Classic winner Rafael Cabrera-Bello cut it back to one with his birdies at the 16th and 17th.
Donaldson had earlier been given a scare by Swede Mikael Lundberg.
Lundberg played the first 10 holes in a remarkable eight under par to charge from six behind to two in front, but then bogeyed the 16th and 18th.
He was nevertheless round in a joint best-of-the-week 65, but Donaldson had a hat-trick of birdies from the second and was two ahead himself before having his first bogey of the day after missing the green at the short 11th.