They’re useful when moulding a new side (4)

I believe the answer is:

dies

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'they're useful when moulding a' is the definition.
The definition suggests an adverb but the answer is not.

'new side' is the wordplay.
'new' is an anagram indicator.
'side' is an anagram of 'DIES'.

Can you help me to learn more?

(Other definitions for dies that I've seen before include "twenty-four hours in Rome" , "Stops working" , "Loses one's life" , "Passes away" , "Coin-stamping tools" .)

I've seen this clue in the Evening Standard.

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