Crossword Genius

A judge can do it up (3)

Ross

I believe the answer is:

sum

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'a judge can' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Perhaps there's a link between them I don't understand?

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for sum that I've seen before include "Amount, aggregate" , "Amount of money; add" , "An additional problem" , "Amount, of money say" , "Amount of money; total" .)

I've seen this clue in the Evening Standard.
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