Swell ultimately cutting boat ride off (5,4)

I believe the answer is:

tidal bore

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'swell ultimately cutting boat ride off' is the definition.
I can't judge whether this definition defines the answer.

'swell ultimately cutting boat ride off' is the wordplay.
'ultimately' says to take the final letters.
'cutting' is an insertion indicator (some letters cut their way into a word).
'off' is an anagram indicator.
The final letter of 'swell' is 'l'.
'boat'+'ride'='boatride'
'boatride' with letters rearranged gives 'tidabore'.
'l' put within 'tidabore' is 'TIDAL BORE'.

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I've seen this clue in The Independent.

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