Make a splash with her in the river (5)

I believe the answer is:

rhine

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

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

'make a splash with her in' is the wordplay.
'her in' can be anagrammed to 'RHINE'.
However, I'm unsure how this is indicated.

'the' acts as a link.

Can you help me to learn more?

(Other definitions for rhine that I've seen before include "Major European river" , "fed by 8 [RHUR]" , "Great European river with Lorelei Rock" , "Great river that flows through Germany" , "River of Cologne" .)

I've seen this clue in the Evening Standard.

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