Port some passed over heading north (6)
I believe the answer is:
odessa
'port' is the definition.
(I've seen this before)
'some passed over heading north' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'heading north' is a reversal indicator.
'assedo' can be found hidden inside 'passed over'.
'assedo' reversed gives 'ODESSA'.
(Other definitions for odessa that I've seen before include "Seaport" , "Ukrainian location" , "Port city on the Black Sea" , "Black Sea location" , "Port city of Ukraine" .)