Submarine, perhaps, making for Kentish port once (8)
I believe the answer is:
sandwich
I believe this clue is a double definition.
'submarine perhaps' is the first definition.
(submarine is a kind of sandwich)
'for kentish port once' is the second definition.
(historical port of Kent)
'making' is the link.
(Other definitions for sandwich that I've seen before include "Golf course - snack" , "seaside town" , "Golf club" , "Maybe double-decker" , "The snack makes strange chin wads" .)