Slight addition to injury makes it worse (6)

I believe the answer is:

insult

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'slight' is the definition.
(to slight someone is to insult or disrespect them)

I can't explain the remainder of the clue.

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(Other definitions for insult that I've seen before include "Remark intended to hurt or humiliate" , "Cause offence to" , "Speak to or treat with disrespect" , "Hurtful and offensive remark" , "Speak or act inm abusive way" .)

I've seen this clue in The Irish Times.

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