Nick, adolescent, making mess (7)
I believe the answer is:
'mess' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'nick adolescent' is the wordplay.
'nick' becomes 'can' (I am not sure about this - if you are sure you should believe this answer much more).
'adolescent' becomes 'teen' (teenager).
'making' acts as a link.
Can you help me to learn more?
(Other definitions for canteen that I've seen before include "Water or cutlery container" , "Water container and works restaurant" , "Box containing cutlery" , "Workers' restaurant" , "somewhere to eat" .)