The matter of children (5)
I believe the answer is:
issue
I believe this is a double definition.
'the matter' is the first definition.
('issue' can be a synonym of 'matter')
'children' is the second definition.
(issue can mean someone's offspring)
'of' acts as a link.
(Other definitions for issue that I've seen before include "Sprogs" , "Come forth or bring out" , "Topic; give out" , "Outflow or point of concern" , "Matter for discussion" .)