There are no children without this (5)
I believe the answer is:
issue
'there are no children without this' is the definition.
The definition suggests a singular noun which matches the answer.
This is all the clue.
Can you help me to learn more?
(Other definitions for issue that I've seen before include "Point under discussion" , "Children, offspring" , "Subject to discuss" , "Important problem" , "Difficulty" .)