Sherlock Holmes or Hercule Poirot (6)
I believe the answer is:
sleuth
'sherlock holmes or hercule poirot' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for sleuth that I've seen before include "Investigator (informal)" , "Hustle like detective (6)" , "Track" , "Hustle (anag)" , "Gumshoe" .)