Empty area (5)
I believe the answer is:
space
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">empty area</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 space that I've seen before include "Unfilled region" , "Free area" , "Blank" , "Empty area, may be outer" , "Interstellar vacuum" .)