Leave-taking word (3)
(Other definitions for bye that I've seen before include "Run scored in cricket from unhit ball" , "Run scored in cricket from a ball that passes batman" , "Extra run in cricket" , "[ADIEU]" , "Extra run; farewell" .)
'leave-taking word' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for adieu that I've seen before include "Comment on leaving" , "Goodbye, mon ami!" , "Fare thee well!" , "the last word in Paris" , "Goodbye in France" .)