She's kept quiet (3)
I believe the answer is:
mum
This might be a double definition.
'she's' is the first definition.
Both the definition and answer are singular nouns.
Perhaps they are linked in a way I don't understand?
'quiet' is the second definition.
(to keep mum is to stay quiet)
'kept' is the link.
Can you help me to learn more?
(Other definitions for mum that I've seen before include "Palindromic mater" , "Parent - shtoom" , "Mother (colloq.)" , "Informal palindromic mother" , "Silence" .)