Rebel fights crossing river? Yes, river (4)
I believe the answer is:
elbe
'river' is the definition.
(I have seen 'River of Germany ' mean 'elbe' so perhaps 'river' could also mean 'elbe')
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for elbe that I've seen before include "River rising in the Czech Republic and flowing into the North Sea" , "Flower" , "Dresden and Hamburg's river" , "Dresden/Hamburg river" , "River flowing through Dresden and Hamburg" .)