Picture designer with a master's degree (7)
I believe the answer is:
diorama
'picture' is the definition.
(diorama is a kind of picture)
'designer with a master's degree' is the wordplay.
'designer' becomes 'dior' (dior is a designer brand).
'with' is a charade indicator (letters next to each other).
'master's degree' becomes 'ma' (MA is an example).
'dior'+'a'+'ma'='DIORAMA'
(Other definitions for diorama that I've seen before include "Three-dimensional series of pictures representing a scene" , "Miniature setting" , "Exhibition" , "AM radio? (anag)" , "Miniature three-dimensional scene" .)