She's in Britain (4)
I believe the answer is:
rita
'she's' is the definition.
'in britain' is the wordplay.
'in' says the answer is hidden in the clue.
'RITA' can be found hidden inside 'britain'.
(Other definitions for rita that I've seen before include "-- Hayworth, US film actress" , "Lovely -- , meter maid (Beatles)" , "subject of education" , "The Beatles' lovely girl" , "Educating - - , film" .)