One with police department enters residence for murder (8)
I believe the answer is:
homicide
'murder' is the definition.
(synonyms)
'one with police department enters residence' is the wordplay.
'one' becomes 'i' (Roman numeral).
'with' is a charade indicator (letters next to each other).
'police department' becomes 'CID' (abbreviation for Criminal Investigation Department).
'enters' means one lot of letters goes inside another.
'residence' becomes 'home' (home is a kind of residence).
'i'+'cid'='icid'
'icid' put inside 'home' is 'HOMICIDE'.
'for' acts as a link.
(Other definitions for homicide that I've seen before include "Serious crime" , "Murder (of one person)" , "The killing of one person by another" , "The killing of one human by another" , "The killing of a human (mainly US)" .)