A must see: Stalin getting overthrown (9)
I believe the answer is:
essential
'a must' is the definition.
(thesaurus)
'see stalin getting overthrown' is the wordplay.
'getting' is a charade indicator (letters next to each other).
'overthrown' indicates anagramming the letters.
'see'+'stalin'='seestalin'
'seestalin' is an anagram of 'ESSENTIAL'.
(Other definitions for essential that I've seen before include "Basic or necessary" , "Vitally important" , "Crucial" , "must-have item" , "So is certain oil-production" .)