Excessively bold oddball I've confronted (13)
I believe the answer is:
overconfident
'excessively bold' is the definition.
(I know that overconfident is a more specific form of the attribute excessively bold)
'oddball i've confronted' is the wordplay.
'oddball' indicates anagramming the letters (I've seen this in other clues).
'ive'+'confronted'='iveconfronted'
'iveconfronted' anagrammed gives 'OVERCONFIDENT'.
(Other definitions for overconfident that I've seen before include "Cock-sure" , "Too bullish" , "Too certain of oneself" , "Too bold or certain" , "Too sure of oneself" .)