Threaten little devil with termination (6)
I believe the answer is:
impend
'threaten' is the definition.
(I've seen this before)
'little devil with termination' is the wordplay.
'little devil' becomes 'imp' (an imp is a little demon).
'with' says to put letters next to each other.
'termination' becomes 'end' (I've seen this in another clue).
'imp'+'end'='IMPEND'
(Other definitions for impend that I've seen before include "Be looming" , "Threaten; approach" , "(Of a bad thing) loom" , "Be imminent or about to happen" , "menace" .)