Communal dining room in an untidy state (4)
I believe the answer is:
mess
I believe this clue is a double definition.
'communal dining room' is the first definition.
(eg in the army)
'an untidy state' is the second definition.
(state of being untidy)
'in' is the link.
(Other definitions for mess that I've seen before include "Dog's breakfast" , "pickle" , "pap" , "difficulty" , "sloppy > food" .)