Stockade in Australia infamous for its gold miners' riot of 1854 (6)
I believe the answer is:
eureka
(Other definitions for eureka that I've seen before include "Triumphant exclamation of discovery" , "Exclamation of triumph" , "Archimedes' cry of triumph as he ran naked through the streets of Syracuse?" , "Cry on a great discovery" , "discovery that's brilliant" .)