Small vehicle by Autobahn, a Beetle (6)
I believe the answer is:
scarab
'a beetle' is the definition.
(scarab is a kind of beetle)
'small vehicle by autobahn' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'vehicle' becomes 'car' (car is a kind of vehicle).
'by autobahn' becomes 'ab' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
's'+'car'+'ab'='SCARAB'
Can you help me to learn more?
(Other definitions for scarab that I've seen before include "crawler" , "Sacred beetle of ancient Egypt" , "Old abuse" , "Holy beetle" , "Beetle regarded as divine by ancient Egyptians" .)