Outrageous cheek without unqualified driver getting to shout abusively (6)
I believe the answer is:
heckle
But I can't explain it at all! Could you help me understand?
(Other definitions for heckle that I've seen before include "Verbally interrupt performer" , "Shout abuse at, a speaker say" , "Jeer or interrupt speaker from crowd" , "Interrupt (a public speaker) with taunts" , "rudely interrupt" .)