After drive, a companion leaves (7)
I believe the answer is:
spinach
'leaves' is the definition.
(leafy vegetable)
'after drive a companion' is the wordplay.
'after' means one lot of letters go next to another.
'drive' becomes 'spin' (I've seen this before).
'companion' becomes 'ch' (Companion of Honour).
'spin'+'a' is 'spina'.
'spina'+'ch'='SPINACH'
(Other definitions for spinach that I've seen before include "Popeye the Sailor's vegetable of choice" , "leaves on plate?" , "something to eat" , "Vegetable plant" , "Popeye the Sailor's favourite vegetable" .)