Spies coming back for items in canteen? (6)
I believe the answer is:
spoons
'items in canteen?' is the definition.
(spoons are used when eating)
'spies coming back' is the wordplay.
'spies' becomes 'snoops' ('snoop' can be a synonym of 'spy').
'coming back' shows that the letters should be reversed in order.
'snoops' backwards is 'SPOONS'.
'for' is the link.
(Other definitions for spoons that I've seen before include "Percussion instrument" , "Runcible eating irons?" , "More than one server" , "Table utensils as for soup" , "courts" .)