Free of what obstructs, and easy to understand. Also to remove — the same word for the state and the act of reaching it.
Old French cler, from Latin clarus (bright, clear, famous); the 'to remove' sense is a later verbal extension of the state of being unobstructed.
Free of what obstructs, and easy to understand — also, as a verb, the act of reaching that state by removing what was in the way.