Driving away after choosing which 50 should leave for Japan (8)
I believe the answer is:
ejecting
'driving away after choosing which 50 should' is the definition.
The answer and definition can be both to do with contact as well as being present participle verbs.
Perhaps you can see a link between them that I can't see?
'leave for japan' is the wordplay.
'leave' becomes 'eject' (ejecting is a kind of leaving).
'for japan' becomes 'ing' (I am not sure about this - if you are sure you should believe this answer much more).
'eject'+'ing'='EJECTING'
Can you help me to learn more?
(Other definitions for ejecting that I've seen before include "Chucking out" , "Throwing out" .)