Incoherent article penned by bishops on ostentatious items (8)
I believe the answer is:
babbling
'incoherent' is the definition.
(thesaurus)
'article penned by bishops on ostentatious items' is the wordplay.
'article' becomes 'a' (indefinite article).
'penned by' indicates putting letters inside.
'bishops' becomes 'bb' (I've seen this in other clues).
'on' says to put letters next to each other.
'ostentatious items' becomes 'bling'.
'a' put within 'bb' is 'bab'.
'bab'+'bling'='BABBLING'
(Other definitions for babbling that I've seen before include "Sounding like a baby (or a brook?)" , "indulging in gas?" , "Talking gibberish" .)