Works canteens containing useless food (10)
I believe the answer is:
sustenance
'food' is the definition.
(sustenance is a kind of food)
'works canteens containing useless' is the wordplay.
'works' indicates anagramming the letters.
'containing' indicates putting letters inside.
'useless' becomes 'us' (abbreviation for unserviceable).
'canteens' anagrammed gives 'stenance'.
'stenance' enclosing 'us' is 'SUSTENANCE'.
(Other definitions for sustenance that I've seen before include "cooking provides this?" , "Nutriment" , "Nourishment" , "Food and drink" .)