Speaker's issue — if so, it makes lout pout? (4)

I believe the answer is:

lisp

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'speaker's issue' is the definition.
(speech impediment)

I don't understand the rest of the clue.

(Other definitions for lisp that I've seen before include "speak imperfectly" , "Non-standard pronunciation" , "Slight speech impediment" , "Be unable to pronounce S" , "Thpeak like thith" .)

I've seen this clue in The Times.

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