Sorry for delay in getting this one on the site. I know the answer (as confirmed in the answers the next day) but don't know how it is built up crypticly.
20across: Old money that may be used in evidence!
answer: Sixpence.
I can see that sixpence is old money, but I don't understand the "may be used in evidence" bit of the clue.
Thank you very much for the explanation which I now understand. That sure is deeply cryptic. You have to get the answer SIXPENCE from the clue, then reinterpret the answer to get VID, then realise that that is part of word evidence.
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