Note kitty's been raised: it's understood (5)
I believe the answer is:
tacit
'understood' is the definition.
(I know that silent can be written as tacit)
'note kitty's been raised' is the wordplay.
'note' becomes 'ti' (musical note as in do re mi fa so la ti).
'kitty' becomes 'cat'.
'been raised' says the letters should be written backwards.
'ti'+'cat'='ticat'
'ticat' written backwards gives 'TACIT'.
'it's' is the link.
(Other definitions for tacit that I've seen before include "Unspoken but implied" , "Implied without being stated" , "Implied or understood, not put into words" , "Silently understood" , "Implicit, unspoken" .)