Crossword Genius

Touch upon sum overdue and outstanding (6)

Ross

I believe the answer is:

allude

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'touch' is the definition.
(I know that touch can be written as allude)

I don't understand the rest of the clue.

Can you help me to learn more?

(Other definitions for allude that I've seen before include "Refer to, speak of" , "Speak about in passing" , "Refer (to) in passing" , "give a reference" , "Refer briefly or indirectly in speaking" .)

I've seen this clue in the Sydney Morning Herald.
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