Crossword Genius

Copper's covering evidence (5)

Ross

I believe the answer is:

proof

'evidence' is the definition.
(proof is a kind of evidence)

'copper's covering' is the wordplay.
'copper' becomes 'p'.
'covering' becomes 'roof' (roof is a kind of covering).
'p'+'roof'='PROOF'

(Other definitions for proof that I've seen before include "Draft copy of printed text" , "Test" , "Evidence that establishes the truth" , "Exposition ending QED?" , "Author may have to check this" .)

I've seen this clue in The Independent.
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