It's goodbye to the Japanese (8)
I believe the answer is:
sayonara
'it's goodbye' is the definition.
(Japanese for 'goodbye')
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for sayonara that I've seen before include "Goodbye or farewell in Japan" , "Japanese valediction" , "Goodbye (Jap.)" , "Japanese goodbye" , "Japanese farewell" .)