The ice astonishes one (5)

I believe the answer is:

rocks

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

I don't understand the remainder of the clue.

(Other definitions for rocks that I've seen before include "Large stones" , "Crags; diamonds" , "Causes shock to; diamonds" , "is brilliant" , "Excites" .)

I've seen this clue in the Evening Standard.

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