Discoverer’s cry (6)
I believe the answer is:
eureka
'discoverer's cry' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for eureka that I've seen before include "Greek cry of discovery by Archimedes" , "alloy" , "discovery that's brilliant" , "Exultant cry" , "Triumphant exclamation of discovery" .)