Black Sea port some passed over heading west (6)
I believe the answer is:
odessa
'black sea port' is the definition.
(Ukrainian port on the Black Sea)
'some passed over heading west' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'heading west' shows that the letters should be reversed in order.
'assedo' is hidden within 'passed over'.
'assedo' in reverse letter order is 'ODESSA'.
(Other definitions for odessa that I've seen before include "Ukrainian location" , "Seaport" , "Black Sea location" , "Do seas come into Ukrainian city?" , "Ukrainian Black Sea port" .)