Couple, heading off, left transport hub (7)
I believe the answer is:
airport
'transport hub' is the definition.
(I've seen this before)
'couple heading off left' is the wordplay.
'couple' becomes 'pair' ('pair' can be a synonym of 'couple').
'heading off' means to remove the first letter.
'left' becomes 'port' (left side of a ship - opposite of starboard).
'pair' with its first letter taken away is 'air'.
'air'+'port'='AIRPORT'
(Other definitions for airport that I've seen before include "Destination for planes" , "Charles de Gaulle, for instance" , "Novel by Arthur Hailey" , "Heathrow, for example" , "Heathrow or similar place" .)