Film backsides of outlandish chimney-sweep (6)

I believe the answer is:

psycho

I'm a little stuck... Click here to teach me more about this clue!

'film' is the definition.
(Alfred Hitchcock film)

I can't explain the rest of the clue.

(Other definitions for psycho that I've seen before include "Nineteen sixty Hitchcock film" , "Alfred Hitchcock thriller" , "Hitchcock's 1960 thriller" , "Norman Bates's film" , "Loony" .)

I've seen this clue in the Sydney Morning Herald.

Want a hint initially instead of a full solution? Install my app