Self-assured novice fronted broadcast (13)
I believe the answer is:
overconfident
'self-assured' is the definition.
(thesaurus)
'novice fronted broadcast' is the wordplay.
'broadcast' indicates anagramming the letters (letters scattered or cast around).
'novice'+'fronted'='novicefronted'
'novicefronted' anagrammed gives 'OVERCONFIDENT'.
(Other definitions for overconfident that I've seen before include "Too bullish" , "Too sure of oneself" , "Cock-sure" , "Too certain of oneself" , "Too bold or certain" .)