Conspiratorial group (5)
I believe the answer is:
cabal
'conspiratorial group' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for cabal that I've seen before include "secret council" , "Camp" , "Small group involved with intrigue" , "Conspiring group" , "Small group of (eg political) plotters" .)