Talk about port transport (7)
I believe the answer is:
chariot
'transport' is the definition.
(I know that chariot is a more specific form of the action the transport)
'talk about port' is the wordplay.
'talk' becomes 'chat' (chat can mean to talk).
'about' means one lot of letters goes inside another.
'port' becomes 'rio' (Rio de Janeiro is a port).
'chat' enclosing 'rio' is 'CHARIOT'.
(Other definitions for chariot that I've seen before include "Stately vehicle" , "Ben Hur's car" , "Vehicle in Ben Hur?" , "coach" , "Two-wheeled horse-drawn vehicle in ancient Rome" .)