Easily understood (5)
'easily understood' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for lucid that I've seen before include "Clear-cut" , "Clear, intelligible" , "Transparently clear" , "Cogent" , "Thinking clearly" .)
(Other definitions for accessible that I've seen before include "Open to be got at" , "able to be reached" , "Easy to talk to; approachable" , "Approachable; easily understood" .)