Clean eating did not come about from ashy bikini lady, it was around a long time before she marketed her version of it.
Clean eating is removing processed/manufactured foods from your diet. Very simply eating real food, no processed sugar, no boxes, no additives. I see various takes on it including people who still live on packaged processed food because it has macro written on it, use low fat products full of thickeners and other toxic rubbish and protein powders. This to me is definitely not clean.
It can be tough to get a grasp on as we have so many frankenfoods that we think are normal, but once you grasp the concept of whole, fresh, non processed food then it is very simple, challenging sometimes when we are surrounded by processed rubbish and misleading dietary information and advertising though..ie low fat products and processed vegetable oils are better for you.
Leaning challenge is a good start point if you can find some information on that. Some good you tubes on it with Soren.