Talk of quiet toy (7)
I believe the answer is:
prattle
'talk' is the definition.
(I know that prattle is a type of cackle)
'quiet toy' is the wordplay.
'quiet' becomes 'p' (music symbol for 'piano', ie soft or quiet).
'toy' becomes 'rattle' (I've seen this before).
'p'+'rattle'='PRATTLE'
'of' is the link.
(Other definitions for prattle that I've seen before include "Foolish talk" , "Childish talk" , "Chatter inconsequentially, natter" , "Talk inanely" , "Chatter inanely" .)