Gang, cabal (6)
I believe the answer is:
clique
I believe this is a double definition.
'gang' is the first definition.
(thesaurus)
'cabal' is the second definition.
(thesaurus)
(Other definitions for clique that I've seen before include "Coterie" , "Inner circle" , "set" , "Group hostile to outsiders" , "Close-knit exclusive group" .)