Sorrow after sound - well I never (4,5)
I believe the answer is:
good grief
'well i never' is the definition.
I don't know anything about this answer so I can't tell whether this works.
'sorrow after sound' is the wordplay.
'sorrow' becomes 'grief' (grief is a kind of sorrow).
'after' is a charade indicator (letters next to each other).
'sound' becomes 'good' (associated in meaning).
'grief' put after 'good' is 'GOOD GRIEF'.
Can you help me to learn more?
(Other definitions for good grief that I've seen before include "Exclamation of surprise or dismay" , "I'm dismayed!" , "Exasperated utterance" , "Oath given surprisingly" .)