At present there are no defined regulations exist that brands must meet in order to claim a clean label product. Anyone can claim clean label, so certain brands have used the term fairly loosely to push their marketing agenda.
At its most basic level, clean label refers to food products that have fewer ingredients, and simpler ingredients at that. It means moving away from highly processed ingredients and toward ingredients from natural sources.
Any type of sugar i.e. "Organic Sugar or Cane Sugar" from a nutritional standpoint is still sugar and most food chemists would not consider it a clean label ingredient. But the health halo created by the clean label movement can still entice consumers into buying a product that is loaded with processed sugar extolling its benefit as "better for you".
Consumption of added sugars is one of the worst and potentially most damaging ingredients in the Western diet. In many studies excessive sugar has shown it may contribute to an increased risk of serious health conditions.