Definite article (3)
I believe the answer is:
the
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">definite article</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for the that I've seen before include "and 24 Down: Similar things" , "Over - - moon" , "That particular one" , "Article is quite definite" , "See 10 Across" .)