How many letters does the top answer for “a city in western germany; industrial center of the ruhr” have?

The most common answer is essen (5 letters).

Crossword clue: a city in western germany; industrial center of the ruhr

1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

essen 5 letters wn-def

a city in western Germany; industrial center of the Ruhr

an industrial city in western germany on the rhine 57% similar → dusseldorf