Slight problem with speech after too much Tignanello? (4)

I believe the answer is:

slur

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'slight' is the definition.
(I've seen this before)

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

(Other definitions for slur that I've seen before include "Disparagement" , "Pronounce indistinctly or speak ill of" , "Slight - smear" , "Slight - stain" , "disgrace" .)

I've seen this clue in The Independent.

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