100th anniversary (9)

I believe the answer is:
centenary
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">100th anniversary</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for centenary that I've seen before include "100th anniversary" , "special occasion" , "celebration" , "significant anniversary" , "One hundredth anniversary" .)