Leaving university begin something outstanding (4)

I believe the answer is:

debt

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'outstanding' is the definition.
(I've seen this before)

I don't understand how the rest of the clue works.

(Other definitions for debt that I've seen before include "Money owed or due" , "Arrears, liability" , "Financial liability" , "state of obligation" , "Sum of money that's owed" .)

I've seen this clue in The Times.

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