Little devil wearing top, transparent (6)
I believe the answer is:
limpid
'transparent' is the definition.
(I know that transparent can be written as limpid)
'little devil wearing top' is the wordplay.
'little devil' becomes 'imp' (I've seen this before).
'wearing' indicates putting letters inside.
'top' becomes 'lid' (lid is a kind of top).
'imp' put within 'lid' is 'LIMPID'.
(Other definitions for limpid that I've seen before include "Completely clear" , "Crystal-clear" , "Clear, like air or water, say?" , "Crystal clear like pure water" , "Clear and transparent, water say" .)