Driver's way off shaping solid par
I believe the answer is:
slip road
'off shaping solid par' is the definition.
Although both the answer and definition are singular nouns, I can't understand how one could define the other.
'driver's way' is the wordplay.
'driver's' becomes 'slip' (I am not sure about this - if you are sure you should believe this answer much more).
'way' becomes 'road' (road is a kind of way).
'slip'+'road'='SLIP-ROAD'
Can you help me to learn more?
(Other definitions for slip road that I've seen before include "Motorway exit or entrance" , "Joining lane" , "Motorway approach or exit" , "Motorway access point" , "Way to leave or join a motorway" .)