Weapon involving terrible risk? (4)
I believe the answer is:
kris
'weapon' is the definition.
(I've seen this before)
'terrible risk?' is the wordplay.
'terrible' indicates an anagram.
'risk' is an anagram of 'KRIS'.
'involving' acts as a link.
(Other definitions for kris that I've seen before include "Malayan dagger" , "Indonesian dagger; sounds like fold" , "weapon" , "Malay knife" , "Malayan slashing knife" .)