Military dining room (4)
I believe the answer is:
mess
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">military dining room</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 mess that I've seen before include "State of disorder" , "Place to eat" , "Chaos, confusion" , "Jumble" , "Untidy confusion" .)