Covering picture (4)
I believe the answer is:
film
I believe this is a double definition.
'covering' is the first definition.
(thesaurus)
'picture' is the second definition.
('film' can be a synonym of 'picture')
(Other definitions for film that I've seen before include "Screen" , "Material for wrapping" , "Cinema celebrity" , "Thin layer - seen on screens" , "Flick" .)