Cleaner receives award from the queen in assembly room (7)
I believe the answer is:
chamber
'assembly room' is the definition.
(eg a parliamentary chamber)
'cleaner receives award from the queen' is the wordplay.
'cleaner' becomes 'char' (charwoman is a type of cleaner).
'receives' indicates putting letters inside (inserted letters are received).
'award from the queen' becomes 'MBE' (Member of the British Empire award).
'char' enclosing 'mbe' is 'CHAMBER'.
'in' is the link.
(Other definitions for chamber that I've seen before include "Room for the judge or the bed" , "Room where a judge transacts business" , "A formal room as for judge" , "boudoir?" , "It may be found in a gun" .)