The Collaborative International Dictionary of English v.0.48:

Briefless \Brief"less\ (br[=e]f"l[e^]s), a.
   Having no brief; without clients; as, a briefless barrister.
   [1913 Webster]

WordNet (r) 3.0 (2006):

briefless
    adj 1: (of lawyers or barristers) lacking clients