Sound of stream in foreign capital (4)

I believe the answer is:

bern

I'm a little stuck... Click here to teach me more about this clue!

'capital' is the definition.
(capital of Switzerland)

I don't understand how the remainder of the clue works.

(Another definition for bern that I've seen is " German name for Swiss capital".)

I've seen this clue in The Guardian.

Want a hint initially instead of a full solution? Install my app