Don't start to talk about baby's toy (6)
I believe the answer is:
rattle
'baby's toy' is the definition.
(I've seen this before)
'don't start to talk' is the wordplay.
'don't start' means to remove the first letter.
'to talk' becomes 'prattle' (prattling is a kind of talking).
'prattle' with its initial letter removed is 'RATTLE'.
'about' acts as a link.
(Other definitions for rattle that I've seen before include "Fluster" , "Sir Simon --, conductor" , "Noisy device < to throw" , "Child's toy; unsettle" , "Disconcert - English conductor, b. 1955" .)