Susie is upset by children (5)
I believe the answer is:
issue
'children' is the definition.
(issue can mean someone's offspring)
'susie is upset' is the wordplay.
'is upset' indicates an anagram (I've seen 'are upset' mean this).
'susie' is an anagram of 'ISSUE'.
'by' is the link.
(Other definitions for issue that I've seen before include "Matter for discussion" , "Point under discussion" , "Point in dispute" , "Pour forth" , "Contentious point" .)