Capital on the Vltava (6)
I believe the answer is:
prague
'capital on the vltava' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for prague that I've seen before include "Capital city of Czech Republic" , "Czech Republic's capital" , "Gear up for this European city" , "Rather quiet" , "European capital" .)