Utters impulsively (6)
I believe the answer is:
blurts
'utters impulsively' is the definition.
('blurt' can be a synonym of 'utter impulsively')
This is all the clue.
(Other definitions for blurts that I've seen before include "Speaks out impulsively" , "Utters abruptly or tactlessly" , "Utters impulsively" .)