On which to drive a generous distance? (7)
I believe the answer is:
freeway
'on which to drive a' is the definition.
I can't judge whether this defines the answer.
'generous distance?' is the wordplay.
'generous' becomes 'free' (I've seen this before).
'distance?' becomes 'way' (way is a kind of distance).
'free'+'way'='FREEWAY'
Can you help me to learn more?
(Other definitions for freeway that I've seen before include "No tolls on this major road!" , "road in US" , "Motorway on which stopping or parking is forbidden" , "Road without tolls" , "American road" .)