Disorder found in room, essentially (4)
I believe the answer is:
mess
'disorder' is the definition.
(I know this)
'in room essentially' is the wordplay.
'in' indicates a hidden word.
'MESS' is hidden in the letters of 'room essentially'.
'found' is the link.
(Other definitions for mess that I've seen before include "State of confusion or untidiness" , "Communal dining room" , "Dog's breakfast" , "pap" , "Dirty or untidy state" .)