Ask for more harmony to culminate libretto, essentially (7)
I believe the answer is:
reorder
'ask for more' is the definition.
I can't judge whether this defines the answer.
'harmony to culminate libretto essentially' is the wordplay.
'harmony' becomes 'order' (order can mean harmony or neatness).
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'culminate libretto essentially' becomes 're' (I can't justify this - if you can you should believe this answer much more).
'order' put after 're' is 'REORDER'.
Can you help me to learn more?
(Other definitions for reorder that I've seen before include "marshal over" , "Send off again for" , "Request for further supply" , "Again apply for" , "Make a further request" .)