Worry, after backing one child’s contact (7)
I believe the answer is:
liaison
'contact' is the definition.
('liaison' can be a synonym of 'contact')
'worry after backing one child's' is the wordplay.
'worry' becomes 'ail' (I've seen this before).
'after backing' is a reversal indicator.
'one' becomes 'i' (Roman numeral).
'child' becomes 'son' (son is a kind of child**).
'ail' back-to-front is 'lia'.
'lia'+'i'+'son'='LIAISON'
(Other definitions for liaison that I've seen before include "A contact or affair" , "Sort of officer" , "carryon" , "Fling - intrigue" , "Connection - relationship" .)