Madness, having uranium near each child (8)
I believe the answer is:
unreason
'madness' is the definition.
'uranium near each child' is the wordplay.
'uranium' becomes 'u' ('U' can be a synonym of 'uranium').
'near' becomes 'nr' (abbreviation used in addresses).
'each' becomes 'ea'.
'child' becomes 'son' (son is a kind of child**).
'u'+'nr'+'ea'+'son'='UNREASON'
'having' is the link.
(Other definitions for unreason that I've seen before include "insanity" , "The absence of rationality or logic" , "foolishness" , "Irrationality" , "nonsense" .)