Better description of a tsunami, possibly (4,6)

I believe the answer is:

high roller

'better' is the definition.
(a high roller bets or gambles a lot of money)

I cannot understand how the remainder of the clue works.

(Other definitions for high roller that I've seen before include "... "tsunami"" , "He takes big risks" , "I bet" .)

I've seen this clue in The Guardian.

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