Black bird crossing a cape to find Polish city (6)
I believe the answer is:
cracow
'polish city' is the definition.
(I've seen this before)
'black bird crossing a cape' is the wordplay.
'black bird' becomes 'crow' (I've seen this before).
'crossing' means one lot of letters goes inside another (to cross can mean to go over or around).
'cape' becomes 'c' (abbreviation used on maps).
'a'+'c'='ac'
'crow' going around 'ac' is 'CRACOW'.
'to find' acts as a link.
(Other definitions for cracow that I've seen before include "Capital at one time" , "foreign city" , "Polish city" , "Former Polish capital" , "E European city" .)