Old vehicle originally carrying deerstalker, say, around port (7)
I believe the answer is:
chariot
'old vehicle' is the definition.
(I've seen this before)
'deerstalker say around port' is the wordplay.
'deerstalker say' becomes 'chat' (I can't explain this - if you can you should give a lot more credence to this answer).
'around' indicates putting letters inside.
'port' becomes 'rio' (Rio de Janeiro is a port).
'chat' going around 'rio' is 'CHARIOT'.
'originally carrying' acts as a link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for chariot that I've seen before include "ride in carriage" , "Vehicle in Ben Hur?" , "four-wheeled carriage?" , "Two-wheeled horse-drawn vehicle in ancient Rome" , "former military vehicle" .)