Composition transposed by non-operatic Co. (5,8)
I believe the answer is:
piano concerto
'composition' is the definition.
I don't know anything about this answer so I cannot tell whether this works.
'transposed by non-operatic co' is the wordplay.
'transposed' indicates anagramming the letters.
'by' means one lot of letters go next to another.
'non'+'operatic'='nonoperatic'
'nonoperatic' after 'co' is 'cononoperatic'.
'cononoperatic' is an anagram of 'PIANO CONCERTO'.
Can you help me to learn more?
(Other definitions for piano concerto that I've seen before include "Keyboard and orchestra work" , "Composition for solo instrument and orchestra" , "The Emperor, for example" .)