German river leading, in essence, to Cologne, do we hear? (4)
I believe the answer is:
oder
'german river' is the definition.
(River Oder in central Europe)
'leading in essence to cologne do we hear?' is the wordplay.
'leading' means one lot of letters go next to another.
'in essence' indicates the central letters.
'do we hear?' becomes 'der' (I can't justify this - if you can you should give a lot more credence to this answer).
The middle of 'cologne' is 'o'.
'o' next to 'der' is 'ODER'.
Can you help me to learn more?
(Other definitions for oder that I've seen before include "River on border of Poland and Germany" , "river, one in central Europe" , "flowing water" , "German river that empties into the Baltic Sea" , "European banker" .)