It’s said in scorn of a large port (3,4)
I believe the answer is:
big deal
'it's said in scorn' is the definition.
I can't judge whether this defines the answer.
'a large port' is the wordplay.
'a large' becomes 'big' (I've seen this before).
'port' becomes 'deal' (I can't justify this - if you can you should give a lot more credence to this answer).
'big'+'deal'='BIG DEAL'
'of' is the link.
Can you help me to learn more?
(Other definitions for big deal that I've seen before include "Successful piece of business (ironical)" , "Potential slam hand at bridge" , "doesn't impress me at all" , "disparaging reply" , "Important transaction - so what!" .)