The meaning of clean usually refers to removing something unwanted: you clean your hands by washing them, then you can clean some grapes.
This word has many meanings related to being pure or empty. You clean a chicken by plucking its feathers, or get cleaned out when you lose all your money at poker. If a drug addict is clean, he's no longer using. You can clean someone’s clock, clean up your act, or clean out a safe and make a clean getaway. If the floor is clean enough to eat off, it's very clean. A clean life is morally pure.