Say nothing, you said, with aristocrat in quarantine (4,3)
I believe the answer is:
shut-off
'quarantine' is the definition.
Both the definition and answer are singular nouns.
Maybe there's a link between them I don't understand?
'say nothing you said with aristocrat' is the wordplay.
'say nothing' becomes 'sh' ('sh' is said to tell someone to say nothing).
'you said' becomes 'U' (homophone of 'you').
'with' is a charade indicator (letters next to each other).
'aristocrat' becomes 'toff' (toff can mean an upper-class person).
'sh'+'u'+'toff'='SHUT-OFF'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for shut-off that I've seen before include "Stop (something) working" , "Safety valve or button" .)