Ridicule piece Joplin would compose (3)
I believe the answer is:
rag
I believe this is a double definition.
'ridicule' is the first definition.
(thesaurus)
'piece joplin would compose' is the second definition.
(ragtime composition, reference to Scott Joplin)
(Other definitions for rag that I've seen before include "Student event" , "Scrap; newspaper (derog.)" , "Duster, perhaps" , "This trade is the clothing business" , "Fun week for college students" .)