Is to take legal action against kids (5)
I believe the answer is:
issue
'kids' is the definition.
(legal term for a person's children)
'is to take legal action against' is the wordplay.
'to take legal action against' becomes 'sue' (I've seen this before).
'is'+'sue'='ISSUE'
(Other definitions for issue that I've seen before include "Sprogs" , "One's offspring" , "Copy of a magazine, for instance" , "Susie (anag.)" , "Important question" .)