Nothing other than transparent (5)
I believe the answer is:
sheer
This clue is a double definition.
'nothing other than' is the first definition.
(I've seen this before)
'transparent' is the second definition.
(I know that transparent can be written as sheer)
(Other definitions for sheer that I've seen before include "Film" , "Utter - precipitous" , "sudden change of direction" , "Clear" , "Mere" .)