Police department (3)
'police department' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for vice squad that I've seen before include "Police unit enforcing gaming and prostitution laws" , "police department" , "section of police force" , "They tackle corruption" .)
'police department' is the definition.
(abbreviation for Criminal Investigation Department)
This is all the clue.