British toast (7)
I believe the answer is:
cheerio
'british toast' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for cheerio that I've seen before include "See you" , "for so long!" , "A hearty farewell, begins with applause" , "Informal goodbye, sounds blithe" , "Bye-bye" .)