Hitchcock film is promoted in three parts? (3,5)
I believe the answer is:
the birds
'hitchcock film' is the definition.
(I've seen this before)
'is promoted in three parts?' is the wordplay.
'is' becomes 'be'.
'promoted' says the letters should be written in reverse (going up, in a down clue).
'in' is an insertion indicator.
'three parts?' becomes 'thirds'.
'be' back-to-front is 'eb'.
'eb' going within 'thirds' is 'THE BIRDS'.
(Other definitions for the birds that I've seen before include "Greek drama" , "Old film" , "1963 Hitchcock film" .)