Elvis’s can sort of rock (9)
I believe the answer is:
jailhouse
'elvis's' is the definition.
Both the answer and definition are singular nouns.
Perhaps you can see a link between them that I don't see?
'can sort of rock' is the wordplay.
'can' becomes 'jail' (The Can is slang for prison).
'sort of rock' becomes 'house' (I can't explain this - if you can you should give a lot more credence to this answer).
'jail'+'house'='JAILHOUSE'
Can you help me to learn more?
(Other definitions for jailhouse that I've seen before include "-- Rock, Elvis Presley movie" , "Southern US prison" , "Prison (USA)" , "Correctional institution" .)