Detectives seen with company in nightclub (5)
I believe the answer is:
disco
'nightclub' is the definition.
(I've seen this before)
'detectives seen with company' is the wordplay.
'detectives' becomes 'dis' (Detective Inspectors, DIs).
'seen with' means one lot of letters go next to another.
'company' becomes 'co' (abbreviation).
'dis'+'co'='DISCO'
'in' is the link.
(Other definitions for disco that I've seen before include "music supplier" , "Style of music/dancing" , "Nightclub with recorded music, in short" , "party for dancers" , "Youngsters' dance venue" .)