Plosive speech sound (7,4)
I believe the answer is:
glottal stop
'plosive speech sound' is the definition.
(glottal stop is a kind of plosive speech sound)
This is all the clue.
(Other definitions for glottal stop that I've seen before include "Sound of mild explosion" , "Consonant sound in some languages" , "(In German) speech sound at start of some vowels" , "Phoneme of some languages (eg, Arabic)" , "Part of Cockney's speech" .)