Rat Scabies finally backing metal singer (8)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

[scabie]S + a reversal (backing) of TIN (metal) + CHER (Crosswordland’s favourite singer – with a  clever ‘lift and separate’ of another singer at the beginning to provide the ‘singer’ in the definition): one of my two top favourite clues I’d like to highlight NIT but that would be stretching it, I think!