Diamond anniversary (8)
I believe the answer is:
sixtieth
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">diamond 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 sixtieth that I've seen before include "One making third score" , "low place?" , "Diamond wedding is one such" , "Anniversary celebrated with diamonds" , "Wedding anniversary designated 'diamond'" .)