Schwarzenegger chasing the lead in major Hitchcock film (6)
I believe the answer is:
marnie
'hitchcock film' is the definition.
(I've seen this in another clue)
'schwarzenegger chasing the lead in major' is the wordplay.
'schwarzenegger' becomes 'arnie' (Arnold Schwarzenegger is nicknamed Arnie).
'chasing' is a charade indicator (letters next to each other) (some letters chase after others).
'the lead in' says to take the initial letters.
The first letter of 'major' is 'm'.
'arnie' after 'm' is 'MARNIE'.
(Other definitions for marnie that I've seen before include "thriller" , "Hitchcock film" .)