WordNet (r) 3.0 (2006):

inner circle
    n 1: an exclusive circle of people with a common purpose [syn:
         clique, coterie, ingroup, inner circle, pack,
         camp]

Moby Thesaurus II by Grady Ward, 1.0:

47 Moby Thesaurus words for "inner circle":
   bunch, bureaucracy, cabal, cadre, camarilla, cell, charmed circle,
   circle, clan, clique, closed circle, coterie, crew, crowd,
   directorate, elite, elite group, group, hierarchy, higher echelons,
   higher-ups, ingroup, junta, junto, management, ministry, mob,
   officialdom, outfit, prelacy, ring, ruling class, ruling classes,
   set, the Establishment, the administration, the authorities,
   the ingroup, the interests, the people upstairs, the power elite,
   the power structure, the top, them, they, top brass, we-group