Good and bad to host initially riotous quiz (5)
I believe the answer is:
grill
'quiz' is the definition.
(subject to questioning)
'good and bad to host initially riotous' is the wordplay.
'good' becomes 'g' (abbreviation).
'and' says to put letters next to each other.
'bad' becomes 'ill' (associated in meaning).
'to host' indicates putting letters inside (inserted letters are hosted or welcomed).
'initially' says to take the initial letters.
The first letter of 'riotous' is 'r'.
'g'+'ill'='gill'
'gill' enclosing 'r' is 'GRILL'.
(Other definitions for grill that I've seen before include "pump" , "rack" , "Framework of metal bars" , "Question hard" , "quiz?" .)