Talk of young affirming their truth enrages right-wing leaders (6)
I believe the answer is:
yatter
'talk' is the definition.
(to yatter is to talk or chatter)
I don't understand how the rest of the clue works.
(Other definitions for yatter that I've seen before include "Go on and on" , "Talk endlessly about nothing" , "Talk incessantly" , "Chatter incessantly (Scots)" , "rabbit on endlessly" .)