Torture giving detectives bit of a shock (8)
I believe the answer is:
distress
'torture' is the definition.
(thesaurus)
'giving detectives bit of a shock' is the wordplay.
'giving' is a charade indicator (letters next to each other).
'detectives' becomes 'dis' (Detective Inspectors, DIs).
'bit of a shock' becomes 'tress' ('shock' can mean a mass of hair).
'dis' next to 'tress' is 'DISTRESS'.
(Other definitions for distress that I've seen before include "grief" , "Extreme anxiety or pain" , "Misery" , "Pain, trouble or sorrow" , "State of anxiety or woe" .)