In confusion, dead wrong to belittle (9)
I believe the answer is:
downgrade
'belittle' is the definition.
(thesaurus)
'in confusion dead wrong' is the wordplay.
'in confusion' is an anagram indicator.
'dead'+'wrong'='deadwrong'
'deadwrong' is an anagram of 'DOWNGRADE'.
'to' acts as a link.
(Other definitions for downgrade that I've seen before include "Sell short" , "Depressed" , "Reduce to lower level" , "Relegate" , "humble" .)