It can make the cat safer, one hears (4)
I believe the answer is:
bell
'it can make the cat safer one hears' is the definition.
The definition suggests a singular noun which matches the answer.
This is the entire clue.
Can you help me to learn more?
(Other definitions for bell that I've seen before include "It's struck by a hammer or clapper" , "Inventor - clanger" , "eg Big Ben" , "inventive fellow" , "It rings when struck" .)