Exclamation of discovery (6)
I believe the answer is:
eureka
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">exclamation of discovery</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for eureka that I've seen before include "Cry of joy on finding something" , "announced by Archimedes" , "Triumphant cry of Greek" , "county seat in 23 [CALIFORNIA]" , ""I've found it!" (Archimedes)" .)