Forces' canteen or shop (5)
I believe the answer is:
naafi
'forces' canteen or shop' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for naafi that I've seen before include "Army canteen or shop" , "Organisation running military canteens" , "place for force-feeding?" , "Military canteen" , "WW2 canteen" .)