"Murder on the Orient Express" detective Hercule (6)
I believe the answer is:
poirot
(Other definitions for poirot that I've seen before include "Hercule --, fictional detective" , "Hercule -, detective (Agatha Christie)" , "Agatha Christie's Belgian detective" , "Hercule . . . . . ., Agatha Christie's detective" , "Fill; live in" .)