River of Central Europe (4)
I believe the answer is:
oder
'river of central europe' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for oder that I've seen before include "East European river" , "River forming northern part of the German-Polish border" , "School blazer insignia" , "River flowing into the Baltic" , "German river that empties into the Baltic Sea" .)