Ocean waves go fast, as before (4,5)

I believe the answer is:

once again

'as before' is the definition.
(I've seen this before)

'ocean waves go fast' is the wordplay.
'waves' is an anagram indicator.
'go fast' becomes 'gain' (as in to gain on someone).
'ocean' is an anagram of 'oncea'.
'oncea'+'gain'='ONCE AGAIN'

(Another definition for once again that I've seen is " encore".)

I've seen this clue in The Guardian.

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