Light in a transparent case (7)
I believe the answer is:
lantern
'light in a transparent case' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for lantern that I've seen before include "Light in a protective casing" , "outside D [DECORATION]" , "Light-admitting structure on roof" , "Case for a light, provides pictures when magic" , "Top of lighthouse" .)