Ring up twice to belittle (4-4)
I believe the answer is:
pooh-pooh
'belittle' is the definition.
(I've seen this in another clue)
'ring up twice' is the wordplay.
'ring up' becomes 'pooh' (I've seen this before).
'twice' says to double the letters.
'pooh' doubled is 'POOH-POOH'.
'to' acts as a link.
(Other definitions for pooh-pooh that I've seen before include "Make dismissive sounds, ridicule repetitively?" , "Dismiss as foolish" , "Dismiss with contempt" , "Disparage - put through hoops" , "Mock, make light of" .)