The capital of Poland (6)
I believe the answer is:
warsaw
'the capital of poland' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for warsaw that I've seen before include "Polands capital" , "Capital of a European Union state" , "European city (with a Convention for commercial flying)" , "1929 international agreement regulating commercial air transport" , "Capital city of Poland" .)