Clutter (4)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">clutter</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 mess that I've seen before include "stew or > jam" , "Clutter" , "Canteen - chaos" , "terrible state" , "Where officers eat" .)