Low-emission vehicle departs, getting permit (5,4)
I believe the answer is:
green card
'permit' is the definition.
(green card is a type of pass or permit)
'low-emission vehicle departs getting' is the wordplay.
'low-emission' becomes 'green' (green can mean good for the environment).
'vehicle' becomes 'car' (car is a kind of vehicle).
'departs' becomes 'd' (abbreviation eg in train timetables).
'getting' is a charade indicator (letters next to each other).
'green'+'car'+'d'='GREEN CARD'
(Another definition for green card that I've seen is " US work and residence permit for foreign nationals".)