City of the Ruhr (5)
I believe the answer is:
essen
'city of the ruhr' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for essen that I've seen before include "German industrial centre" , "German industrial city on the Ruhr" , "Industrial city of northwest Germany" , "European city" , "Krupp HQ (Ger.)" .)