Honour to be in cleaner room (7)
I believe the answer is:
chamber
'room' is the definition.
(chamber is a kind of room)
'honour to be in cleaner' is the wordplay.
'honour' becomes 'mbe'.
'to be in' means one lot of letters goes inside another.
'cleaner' becomes 'char' (charwoman is a type of cleaner).
'mbe' inserted into 'char' is 'CHAMBER'.
(Other definitions for chamber that I've seen before include "Compartment" , "Official room" , "boudoir?" , "It may be found in a gun" , "vault" .)