WordNet sense 1 ((of sound or color) free from anything that dulls or dims):

clean, light

WordNet sense 2 (free of extraneous elements of any kind):

pure

WordNet sense 3 (free from clouds):

cloudless

WordNet sense 4 (free from clouds or mist or haze):

clear

WordNet sense 5 (not mentally confused; able to think clearly and act intelligently):

clearheaded, clear-thinking