Full of chutzpah (5)
I believe the answer is:
'full of chutzpah' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for brash that I've seen before include "forward" , "Foolhardy" , "Flashy, crude" , "Tasteless; rudely confident" , "Audacious" .)