Covered up by Cesare Borgia's houppelande, for instance (4)

I believe the answer is:

robe

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'instance' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.

I can't explain the rest of the clue.

Can you help me to learn more?

(Other definitions for robe that I've seen before include "Formal vestment" , "Old cloak for Boer" , "Ceremonial garment, clothe" , "Loose outer garment" , "habit" .)

I've seen this clue in the Irish Times.

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