Group of Chicago CSI detectives going over nightclub (5)
I believe the answer is:
disco
'nightclub' is the definition.
(a disco is a club for dancing)
'group of chicago csi detectives going over' is the wordplay.
'group of' indicates a hidden word (group of letters from the clue).
'going over' says the letters should be written backwards.
'ocsid' is hidden in the letters of 'chicago csi detectives'.
'ocsid' reversed gives 'DISCO'.
(Other definitions for disco that I've seen before include "lively entertainment, for some?" , "Place to dance to recorded music, in short" , "Nightclub with dancing to recorded music" , "Modern dance hall or event, in brief" , "Dance hall - music by Donna Summer and the Bee Gees, say" .)