Something left out (8)
I believe the answer is:
omission
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">something left out</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 omission that I've seen before include "Exclusion" , "Something lacking" , "Oversight, piece of work neglected" , "A thing left out" , "Leaving-out, oversight" .)