Clean eating to me is very in depth. As mentioned above, a lot of it is being able to recognize the foods you are eating and pronounce them as well. For me it is all about protein and carbs. I do not mind the few fats every day I eat, because lets face it. Unless you are getting ready for a competition, fats are needed by the body. A typical breakfast for me is roughly 90g of protein, 120g of carbs and about 15g of fats. I have about a 3 hour window from eating breakfast to when I get to work. So it helps carry me over and keep me full until I get to work.
Then I eat a carb heavy snack. Because it will be another 3 hours before I can eat again. So at about 9, I eat a protein heavy and carb heavy break. Usually consists of chicken, turkey or ground meat with mashed potatoes and a veggie. Along with 2, 16oz bottles of water. Then lunch comes at 12 and it is another carb and protein heavy meal. Basically the same thing I ate for break, I eat for lunch. I prep them every morning before work, something about cooking it that day makes it taste better than to of cooked it days before and kept inside the fridge.
Then I get off at 3 and snack pretty good. Almonds, cashews or walnuts. A few handfuls. Mondays and Wed are my long nights with several classes after work. So I eat in between classes. Usually just a bit ass glob of mashed potatoes and a veggie. Then when I finally get home, my wife has dinner cooked and I eat that and then snack a bunch while I do homework and get ready for bed.
All in all, I do not go too far off track with the way I eat. I try and eat for what my body needs, and I have become very good and being able to tell what my body needs. My job is very physical and I find myself going up and down 5+ flights of stairs 20-40 times a day carrying 50+lbs at a time the majority of the time. So carbs are very helpful for me. But just be mindful of what you eat. There is no magic trick to eating right.
A good place to start is to look up say, Jay Cutlers, meal prep. And pull a few things from what he eats and incorporate that into your diet. But I stick to the tried and true, protein and carb heavy diets to build mass. Cause fuck it, I do not mind the little belly I have if I am hitting 335 on bench for reps.