Back from Niagara once more (5)

I believe the answer is:

again

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'once more' is the definition.
(synonyms)

'back from niagara' is the wordplay.
'AGAIN' is hidden back-to-front in amongst the letters.
However, I'm not sure how this is indicated.

Can you help me to learn more?

(Other definitions for again that I've seen before include "Next time" , "Ocne more" , "second term" , "return" , "Here we go ___" .)

I've seen this clue in the Evening Standard.

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