Containing nothing (5)
I believe the answer is:
empty
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">containing nothing</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 empty that I've seen before include "Vacant - futile - blank" , "Cleared out" , "Arabic quarter" , "Unoccupied" , "Loneliness parents feel when their children leave home" .)