Erode cover for ducks on English river (4,4)

I believe the answer is:

wear down

'erode' is the definition.
(thesaurus)

'cover for ducks on english river' is the wordplay.
'cover for ducks' becomes 'down' (down feathers).
'on' means one lot of letters go next to another.
'english river' becomes 'wear' (river in the north east of England).
'down' put after 'wear' is 'WEAR DOWN'.

(Another definition for wear down that I've seen is " Gradually erode".)

I've seen this clue in The Times.

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