Modern centre for fresh water (4)

I believe the answer is:

oder

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'fresh water' is the definition.
'Oder' can be an answer for 'water' (Oder is an example). I'm unsure of the 'fresh' bit.

'modern centre' is the wordplay.
'centre' means to look at the middle letters.
The centre of 'modern' is 'ODER'.

'for' acts as a link.

Can you help me to learn more?

(Other definitions for oder that I've seen before include "German river that empties into the Baltic Sea" , "European flower" , "River that, with the Neisse, forms the German-Polish border" , "German and Polish river" , "River on border of Poland and Germany" .)

I've seen this clue in the Evening Standard.

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