Internal security has to prosecute children (5)
I believe the answer is:
issue
'children' is the definition.
(issue can mean someone's offspring)
'internal security has to prosecute' is the wordplay.
'internal security' becomes 'is' (this could be a standard abbreviation which I don't know about).
'has' is a charade indicator (letters next to each other).
'to prosecute' becomes 'sue' (I've seen this before).
'is'+'sue'='ISSUE'
Can you help me to learn more?
(Other definitions for issue that I've seen before include "Matter of dispute" , "Outcome - children" , "Contentious subject" , "Offspring, or the point in question" , "hot potato?" .)