clear (adj.) Look up clear at Dictionary.com
late 13c., "bright," from Old French cler "clear" (of sight and hearing), "light, bright, shining; sparse" (12c., Modern French clair), from Latin clarus "clear, loud," of sounds; in transferred use, of sights, "bright, distinct;" also "illustrious, famous, glorious" (source of Italian chiaro, Spanish claro), from PIE *kle-ro-, from root *kele- (2) "to shout" (see claim (v.)).

The sense evolution involves an identification of the spreading of sound and the spreading of light (cf. English loud, used of colors; German hell "clear, bright, shining," of pitch, "distinct, ringing, high"). Of the weather, from late 14c.; of meanings or explanations, c.1300. (An Old English word for this was sweotol "distinct, clear, evident".) Sense of "free from encumbrance," apparently nautical, developed c.1500. Phrase in the clear attested from 1715.
clear (v.) Look up clear at Dictionary.com
late 14c., "to enlighten," from clear (adj.). Meaning "to leap clear over" is first attested 1791. Related: Cleared; clearing.