A taxi (3)
I believe the answer is:
cab
'a taxi' is the definition.
(I know that taxi can be written as cab)
This is all the clue.
(Other definitions for cab that I've seen before include "'The authority collects money made from crime, initially (3)'" , "It has the authority to confiscate the proceeds of crime, in short" , "info for citizens provided here" , "Hackney" , "Taxi to hold an engine-driver" .)