Readily understood, clear (5)
I believe the answer is:
lucid
I believe this is a double definition.
'readily understood' is the first definition.
(I've seen this before)
'clear' is the second definition.
(similar in meaning)
(Other definitions for lucid that I've seen before include "Easily understood; sane" , "Able to think clearly" , "Limpid" , "Rational, clear" , "Clear, easily understood" .)