Suffer defeat in court room (6)
I believe the answer is:
closet
'room' is the definition.
(I know that closet is a type of room)
'suffer defeat in court' is the wordplay.
'suffer defeat' becomes 'lose' (I've seen this in another clue).
'in' indicates putting letters inside.
'court' becomes 'ct' (abbreviation used in road names).
'lose' inserted inside 'ct' is 'CLOSET'.
(Other definitions for closet that I've seen before include "Small room or wardrobe" , "A small room or cupboard" , "little room" , "Compartment for clothing in the US" , "Shut away in private conference - in small room?" .)