This canteen is in an untidy condition (4)
I believe the answer is:
mess
I believe this clue is a double definition.
'this canteen' is the first definition.
(I've seen this before)
'an untidy condition' is the second definition.
(I've seen this in another clue)
'is in' is the link.
(Other definitions for mess that I've seen before include "Clutter" , "dish" , "Where those who serve eat" , "hash" , "Canteen - muddle" .)