X-rated opening cut from mafia film excerpt (7)
I believe the answer is:
obscene
'x-rated' is the definition.
(X-rated means pornographic)
'opening cut from mafia film excerpt' is the wordplay.
'opening cut from' means to remove the first letter.
'mafia' becomes 'mob' (informal term for the mafia).
'film excerpt' becomes 'scene' (part of a film).
'mob' with its initial letter taken away is 'ob'.
'ob'+'scene'='OBSCENE'
(Other definitions for obscene that I've seen before include "Pseudonym" , "Offensive - indecent" , "Rude" , "Salacious" , "offending sensibilities?" .)