Bathroom, in Britain (3)
I believe the answer is:
loo
'bathroom in britain' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for loo that I've seen before include "In which one goes" , "WC - old card game" , "Card-game" , "A colloquial toilet" , "The little room - card game" .)