Crossword Genius

Copper's covering evidence (5)

Ross

I believe the answer is:

'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 "Specimen", "Conclusive demonstration", "may need amending", "a writer may check", "Render impervious (to)".)

I've seen this clue in The Independent.