Mare's-nest (4)
I believe the answer is:
mess
'mare's-nest' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for mess that I've seen before include "Untidy confusion" , "Where sailors eat" , "Where soldiers may eat" , "State of confusion or untidiness" , "Officers' restaurant - what a dump" .)