Gruff detective taking over (6)
I believe the answer is:
morose
'gruff' is the definition.
(thesaurus)
'detective taking over' is the wordplay.
'detective' becomes 'morse' (I've seen this before).
'taking' indicates putting letters inside.
'over' becomes 'o' (cricket abbreviation).
'morse' placed around 'o' is 'MOROSE'.
(Other definitions for morose that I've seen before include "Sullen and gloomy" , "Gloomy and unsociable" , "Glum or sour-tempered" , "Sad" , "Sullen, crabby" .)