One not having paid to travel, bailiffs finally take vehicle to pound (8)
I believe the answer is:
stowaway
'one not having paid to travel' is the definition.
'bailiffs finally take vehicle to pound' is the wordplay.
'finally' indicates one should take the final letters.
'take vehicle to pound' becomes 'towaway'.
The last letter of 'bailiffs' is 's'.
's'+'towaway'='STOWAWAY'
(Other definitions for stowaway that I've seen before include "Person hiding in a lifeboat?" , "Concealed traveller" , "Person hiding on ship" , "Illegal ship's passenger" , "Free rider" .)