The Collaborative International Dictionary of English v.0.48:

Eclaircissement \E*clair"cisse*ment\, n. [F., fr. ['e]claircir.
   See Eclaircise, v. t.]
   The clearing up of anything which is obscure or not easily
   understood; an explanation.
   [1913 Webster]

         The eclaircissement ended in the discovery of the
         informer.                                --Clarendon.
   [1913 Webster]