Evil grins indicate coating with precious metal (9)

I believe the answer is:

silvering

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'coating with precious metal' is the definition.
The definition and answer can be both to do with contact as well as being present participle verbs.
Maybe there's an association between them I don't understand?

'evil grins indicate' is the wordplay.
'evil grins' anagrams to 'SILVERING'.
However, I'm unsure how this is indicated.

Can you help me to learn more?

I've seen this clue in The Irish News.

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