When someone makes the choice to eat "clean" they are choosing to eliminate all processed foods and extra additives from their diet. Basically, you are choosing to eat whole, unrefined foods.
The basics of eating clean include - eating lots of fruits and vegetables. These are straight from nature - the idea is to stay away from anything that may have been altered in any way.
Include meats, however; "whole" meats that you have chosen straight from the butcher or prepared yourself. You would be very surprised to find out what is actually in ground turkey.
Enjoy whole grains - these are grains that are still complete and haven't been broken down in any form. Examples include: brown rice, whole wheat and other whole grains. You will have to get used to reading over food labels. Just because a product says its "whole grain" does not mean it is. It also does not mean they have not added a bunch of other ingredients as well.
Eat fewer ingredients - try not to purchase items with more than 4-6 ingredients in the ingredient list. Also, be sure you recognize every ingredient. If you can't pronounce it, you probably shouldn't put it in your body.