Simple but revealing (5)
I believe the answer is:
sheer
I believe this clue is a double definition.
'simple' is the first definition.
(I've seen this before)
'revealing' is the second definition.
(thesaurus)
'but' acts as a link.
(Other definitions for sheer that I've seen before include "needing to change a course" , "Arrant" , "Utter - precipitous" , "Completely" , "Clear" .)