At risk, support melting away? (2,4,3)

I believe the answer is:

on thin ice

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

I don't understand how the rest of the clue works.

(Other definitions for on thin ice that I've seen before include "In a risky situation" , "Experiencing treacherous wintry conditions" , "At risk" , "In a delicate situation" , "In a dangerous situation" .)

I've seen this clue in The Telegraph.

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