Stupid, moving cars south (5)
I believe the answer is:
crass
'stupid' is the definition.
(I've seen this in another clue)
'moving cars south' is the wordplay.
'moving' indicates an anagram (letters are moved around).
'south' becomes 's' (abbreviation).
'cars' with letters rearranged gives 'cras'.
'cras'+'s'='CRASS'
(Other definitions for crass that I've seen before include "Boorish about scars" , "Tactless, boorish" , "Grossly stupid, tactless" , "Unrefined" , "Witless" .)