Threaten prankster with death (6)
I believe the answer is:
impend
'threaten' is the definition.
(thesaurus)
'prankster with death' is the wordplay.
'prankster with' becomes 'imp' (I can't justify this - if you can you should give a lot more credence to this answer).
'death' becomes 'end' ('end' can be a synonym of 'death').
'imp'+'end'='IMPEND'
Can you help me to learn more?
(Other definitions for impend that I've seen before include "seen to be around the corner" , "Be about to take place" , "menace" , "Threaten - be about to happen" , "Threaten; approach" .)