Said “A mere outward show,” which does offend (7)

I believe the answer is:

affront

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'offend' is the definition.
(affronting is a kind of offending)

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

Can you help me to learn more?

(Other definitions for affront that I've seen before include "Deliberate insult or show of disrespect" , "A slight" , "Insult, offend" , "Indignity" , "Cause of outrage or offence" .)

I've seen this clue in the Evening Standard.

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