Frivolous extras like percussion and wind instruments (5,3,8)
I believe the answer is:
bells and whistles
'frivolous extras like percussion and wind instruments' is the definition.
I don't know anything about this answer so I can't judge whether this works.
'percussion and wind instruments' is the wordplay.
'percussion' becomes 'bells' (I am not sure about this - if you are sure you should believe this answer much more).
'wind instruments' becomes 'whistles' (whistle is a kind of wind instrument).
'bells'+'and'+'whistles'='BELLS AND WHISTLES'
Can you help me to learn more?
(Other definitions for bells and whistles that I've seen before include "the basic model may be lacking" , "Sound warnings" .)