If clean and clear are used as adjectives: CLEAN: (adj.) free from dirt, marks; not dirty Ex. Take a CLEAN sheet of paper. CLEAR: (adj.) (1) free from obstruction; (2) very obvious or easily understood Ex. (1) Keep the passage CLEAR. (2) She gave a CLEAR explanation.

clean means not dirty. For example, I washed the dishes and now they are clean. Clear can mean different things according to the context. For example, is the road ahead clear? Would you clear the table for me? It's clear you don't understand etc