One taking advantage of a vehicle ferry regularly (6)
I believe the answer is:
abuser
'one taking advantage' is the definition.
(abuse can mean to exploit or take advantage of)
'a vehicle ferry regularly' is the wordplay.
'vehicle' becomes 'bus' (bus is a kind of vehicle).
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
The alternating letters of 'ferry' are 'er'.
'a'+'bus'+'er'='ABUSER'
'of' is the link.
(Other definitions for abuser that I've seen before include "one who uses bad language" , "He takes undue advantage" , "One who reviles or a misuser of drugs" , "Bully" , "Person who over-indulges in, say, drugs or drink" .)