Bother! That means there's a baby in the house! (6)
I believe the answer is:
rattle
'bother' is the definition.
(thesaurus)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for rattle that I've seen before include "Trivial talk" , "Baby's toy; irritate" , "Child's toy; unsettle" , "Baby's toy; sound of something loose" , "not to compose" .)