Clean eating generally means no junk. All whole foods, minimally processed and mostly fresh and unaltered. For example, veggies, fruit, meats if you eat them, eggs, nuts, whole grains only. Herbs. Cold-pressed oils.
As far as abs, I am of the "they are just another muscle" school of thought. I basically do abs on alternating days. Sometimes planks and stability ball, sometimes more traditional stuff. I am a pear so am blessed with no bodyfat in the abs and they are very flat and cut even though I do not work them everyday. But I have been working them for 20 years, maybe more. And I am only 5-10 pounds over "perfect". All of the extra crappola, of course, is in my upper thighs area as befits a pear.