City in the Ruhr, home to the Zollverein coal mine, now part of a Unesco world heritage site (5)

I believe the answer is:

essen

(Other definitions for essen that I've seen before include "city in the Ruhr valley" , "German industrial city on the Ruhr" , "Main industrial city of the Ruhr" , "Krupp HQ (Ger.)" , "Industrial centre of the Ruhr" .)

I've seen this clue in The Times.

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