Break open the port (5)
I believe the answer is:
split
I believe this clue is a double definition.
'break open' is the first definition.
(synonyms)
'the port' is the second definition.
(I've seen this before)
(Other definitions for split that I've seen before include "Cavil" , "European city" , "shared by a couple?" , "Fork" , "Adriatic port" .)