River with a bore? (4)

I believe the answer is:

ebro

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

'river' is the definition.
(I know that Ebro is a river)

'a bore?' is the wordplay.
'bore' anagrams to 'EBRO'.
However, I'm unsure how the anagram is indicated.

'with' acts as a link.

Can you help me to learn more?

(Other definitions for ebro that I've seen before include "Spanish river" , "River of northeast Spain" , "flower" , "European river" , "Longest river in Spain" .)

I've seen this clue in the Evening Standard.

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