Opera about English ship, and German aria (6,5)
I believe the answer is:
nessun dorma
'aria' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'opera about english ship and german' is the wordplay.
'opera' becomes 'norma' (I've seen this in another clue).
'about' means one lot of letters goes inside another.
'english' becomes 'E' (abbreviation).
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'and german' becomes 'und' ('and' in German).
'e'+'ss'+'und'='essund'
'norma' enclosing 'essund' is 'NESSUN DORMA'.
Can you help me to learn more?
(Other definitions for nessun dorma that I've seen before include "Well-known aria from Turandot" , "air" , "Aria from Puccini's opera Turandot" , "Famous Puccini aria (Turandot)" .)