Agency (6)
'agency' is the definition.
(thesaurus)
This is the entire clue.
(Other definitions for medium that I've seen before include "Spiritualist in charge of seance" , "Person who purports to communicate with the dead" , "Average kind of spiritualist" , "Average or intermediate" , "Moderate - agency - channel of communication" .)
'agency' is the definition.
(I know that agency can be written as bureau)
This is the entire clue.
(Other definitions for bureau that I've seen before include "Writing desk with drawers" , "Government department, agency" , "Foreign office" , "The B in the FBI" , "Room" .)