Possible Clues:

• River that empties into the Baltic Sea
• River subject of a 1990 German/Polish treaty
• River that runs through 86-Across
• River which forms part of the border between Germany and Poland
• River in central Europe that forms part of the boundary between Poland and Germany
• Outright order for a European banker
• River of Wroclaw
• Reported fragrance of European flower
• __-Neisse Line, western border of 42-Across
• Smelly-sounding Central European river