With a bit of luck, I'd get clear (5)
I believe the answer is:
lucid
'clear' is the definition.
(similar in meaning)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for lucid that I've seen before include "Able to think clearly" , "Clear-cut" , "Intellectually bright" , "Bright; sane" , "Easy to understand, clearly expressed" .)