Arrogance shown in an RC feast? (10)

I believe the answer is:

assumption

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'feast?' is the definition.
(I have seen 'Catholic feast' mean 'assumption' so perhaps 'feast' could also mean 'assumption')

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

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(Other definitions for assumption that I've seen before include "Belief" , "Summer feast" , "Catholic feast" , "taken for granted" , "Church festival" .)

I've seen this clue in The Independent.

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