Armed services canteen (5)
I believe the answer is:
naafi
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">armed services canteen</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 naafi that I've seen before include "Military canteen" , "Army canteen/shop" , "Organisation running military canteens" , "Military facility" , "Forces' canteen or shop" .)