California's impounding Republican vehicles (4)
I believe the answer is:
cars
'vehicles' is the definition.
(car is a kind of vehicle)
'california's impounding republican' is the wordplay.
I cannot really understand how this works, but
'republican' could be 'r' (political abbreviation) and 'r' is found within the answer.
'california's' could be 'cas' (abbreviation) and 'cas' is located in the remaining letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for cars that I've seen before include "Private vehicles" , "... when these may be driven?" , "Automobiles" , "Motor vehicles" .)