Some postcodes, say, in port (6)
I believe the answer is:
odessa
'port' is the definition.
(Odessa is a Ukrainian port)
'some postcodes say in' is the wordplay.
'some' says the answer is hidden in the clue (some parts of the word are used).
'ODESSA' can be found hidden inside 'postcodes say in'.
(Other definitions for odessa that I've seen before include "Ukrainian naval base" , "Do seas come into Ukrainian city?" , "Port city on the Black Sea" , "Ukrainian Black Sea port" , "Port city of Ukraine" .)