Empty plain (5)
I believe the answer is:
clear
I believe this is a double definition.
'empty' is the first definition.
(thesaurus)
'plain' is the second definition.
(I've seen this before)
(Other definitions for clear that I've seen before include "Lucid, obvious" , "Leap over" , "Exculpate" , "Pellucid" , "Patent" .)