Cocky, big-headed and impetuous (5)
I believe the answer is:
brash
'cocky' is the definition.
(I've seen this before)
'big-headed and impetuous' is the wordplay.
'big-headed' becomes 'b' (this could be a standard abbreviation of which I'm unaware).
'and' says to put letters next to each other.
'impetuous' becomes 'rash' (I've seen this before).
'b'+'rash'='BRASH'
Can you help me to learn more?
(Other definitions for brash that I've seen before include "loose broken rock" , "Flashy, crude" , "Very loud, flashy or showy" , "Tasteless; rudely confident" , "Offensively loud" .)