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' means one lot of letters go next to another.
'bad' becomes 'ill' (similar in meaning).
'to host' indicates putting letters inside (inserted letters are hosted or welcomed).
'initially' indicates taking the first letters.
The initial 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?" .)