Hitchcock film in three equal parts about English bishop (3,5)
I believe the answer is:
the birds
'hitchcock film' is the definition.
(Alfred Hitchcock film)
'three equal parts about english bishop' is the wordplay.
'three equal parts' becomes 'thirds' (I've seen this before).
'about' means one lot of letters goes inside another.
'english' becomes 'e' (abbreviation).
'bishop' becomes 'b' (abbreviation used in chess).
'e'+'b'='eb'
'thirds' going around 'eb' is 'THE BIRDS'.
'in' acts as a link.
(Other definitions for the birds that I've seen before include "Greek drama" , "Old film" , "1963 Hitchcock film" .)