Intermittently rougher part of Germany (4)

I believe the answer is:

ruhr

'part of germany' is the definition.
(I know this)

'intermittently rougher' is the wordplay.
'intermittently' means one should take alternating letters.
The alternate letters of 'rougher' are 'RUHR'.

(Other definitions for ruhr that I've seen before include "Ger. industrial region" , "River and industrial region of northwest Germany" , "Part of Germany" , "German industrial region" , "Rhine tributary, coal district" .)

I've seen this clue in The Independent.

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