Reducing din before screening popular movies regularly (9)
I believe the answer is:
antinoise
'reducing din' is the definition.
(din means noise or disturbance)
'before screening popular movies regularly' is the wordplay.
'before' becomes 'ante' (prefix meaning before).
'screening' means one lot of letters goes inside another (inserted letters are covered or screened by others).
'popular' becomes 'in' ('in' can mean trendy).
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
The alternate letters of 'movies' are 'ois'.
'in'+'ois'='inois'
'ante' enclosing 'inois' is 'ANTINOISE'.
(Another definition for antinoise that I've seen is " against shouting?".)