Leave out of room itself (4)
I believe the answer is:
omit
'leave out' is the definition.
(synonyms)
'of room itself' is the wordplay.
'of' indicates a hidden word.
'OMIT' is hidden within 'room itself'.
(Other definitions for omit that I've seen before include "Leave out or overlook" , "Leave out or fail to do" , "Drop" , "Exclude; veto" , "Leave out, perhaps in error" .)