Juan's goodbye (5)
I believe the answer is:
adios
'juan's goodbye' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for adios that I've seen before include "Adieu, arrivederci" , "Goodbye, amigo" , "so long abroad" , "Bye-bye (amigo)" , "Goodbye (20 across)" .)