Cologne divider (5)
I believe the answer is:
rhine
'cologne divider' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for rhine that I've seen before include "water" , "Ring river (Wagner)" , "Great German river with Lorelei Rock" , "Flower" , "fed by 8 [RHUR]" .)