Ridicule backing band twice (4-4)
I believe the answer is:
pooh-pooh
'ridicule' is the definition.
(I've seen this before)
'backing band twice' is the wordplay.
'backing' says the letters should be written backwards.
'band' becomes 'hoop' (hoop is a kind of band).
'twice' indicates the doubling of some letters.
'hoop' written backwards gives 'pooh'.
'pooh' duplicated is 'POOH-POOH'.
(Other definitions for pooh-pooh that I've seen before include "Dismiss (something) rather contemptuously" , "Dismiss with contempt" , "Mock, make light of" , "Slight" , "Disparage - put through hoops" .)