Threaten little devil with death (6)
I believe the answer is:
impend
'threaten' is the definition.
(thesaurus)
'little devil with death' is the wordplay.
'little devil' becomes 'imp' (I've seen this before).
'with' says to put letters next to each other.
'death' becomes 'end' ('end' can be a synonym of 'death').
'imp'+'end'='IMPEND'
(Other definitions for impend that I've seen before include "Threaten; approach" , "(Of a bad thing) loom" , "Be looming" , "seen to be around the corner" , "Be about to take place" .)