Fellow challenging no good official (8)
I believe the answer is:
mandarin
'official' is the definition.
(mandarin is a kind of official)
'fellow challenging no good' is the wordplay.
'fellow' becomes 'man' (I've seen this before**).
'challenging' becomes 'daring' (daring is a kind of challenging).
'no' is a deletion indicator.
'good' becomes 'g' (abbreviation).
'daring' with 'g' removed is 'darin'.
'man'+'darin'='MANDARIN'
(Other definitions for mandarin that I've seen before include "Variety of citrus fruit" , "top official" , "Small citrus fruit" , "High-ranking public official" , "Reddish-orange, loose-skinned citrus fruit" .)