He wanted more surprising end, say, after finale of concerto on organ (6,5)
I believe the answer is:
oliver twist
'he wanted more surprising end say after finale' is the definition.
The definition suggests a singular noun which matches the answer.
'of concerto on organ' is the wordplay.
'of' becomes 'o''.
'concerto' becomes 'twist' (I can't justify this - if you can you should believe this answer much more).
'on' says to put letters next to each other.
'organ' becomes 'liver' (liver is a kind of organ).
'twist' after 'liver' is 'livertwist'.
'o'+'livertwist'='OLIVER TWIST'
Can you help me to learn more?
(Other definitions for oliver twist that I've seen before include "Eponymous Dickensian character" , "Literary work" , "One wanting more" , "Orphan recruited by criminal gang" , "Dickens eponymous hero" .)