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Sydney University tarnished when kept up thus (9)

Ross

I believe the answer is:

sustained

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'kept up thus' is the definition.
I can't tell whether this definition defines the answer.

'sydney university tarnished' is the wordplay.
'sydney university' becomes 'su' (this could be a standard abbreviation I've not previously seen).
'tarnished' becomes 'stained' (synonyms).
'su'+'stained'='SUSTAINED'

'when' is the link.

Can you help me to learn more?

(Other definitions for sustained that I've seen before include "Steady" , "bore" , "prolonged" , "Long drawn-out" , "Kept going, supported" .)

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