Aria part reduced emperor to scull Arabic port (7)
I believe the answer is:
cadenza
'aria part' is the definition.
(I've seen this in another clue)
'reduced emperor to scull arabic port' is the wordplay.
I cannot really see how this works, but
'port' could be 'aden' (port in Yemen) and 'aden' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for cadenza that I've seen before include "Solo display passage" , "Virtuoso passage in concerto, etc" , "Virtuoso passage for soloist in a concerto" , "Virtuoso performance" , "Impromptu insertion in piece of music" .)