Ruin arrangement of Schubert, omitting soprano (7)
I believe the answer is:
butcher
'ruin' is the definition.
(thesaurus)
'arrangement of schubert omitting soprano' is the wordplay.
'arrangement of' indicates an anagram.
'omitting' suggests deleting specific letters.
'soprano' becomes 's' (musical abbreviation).
'schubert' with 's' taken away is 'chubert'.
'chubert' with letters rearranged gives 'BUTCHER'.
(Other definitions for butcher that I've seen before include "Meat purveyor" , "Less like lamb" , "Meat supplier" , "Kill - food retailer" , "Slaughter" .)