A dagger is a source of risk (4)
I believe the answer is:
kris
'a dagger' is the definition.
(I've seen this before)
'source of risk' is the wordplay.
'source of' is an anagram indicator.
'risk' is an anagram of 'KRIS'.
'is a' acts as a link.
(Other definitions for kris that I've seen before include "Its flag has a maple leaf" , "Wavy-edged dagger" , "Indonesian dagger; sounds like fold" , "Malayan slashing knife" , "Malay dagger - for Kristofferson?" .)