Threaten island legislator with death (6)
I believe the answer is:
impend
'threaten' is the definition.
(I've seen this in another clue)
'island legislator with death' is the wordplay.
'island legislator' becomes 'imp' (I can't justify this - if you can you should give a lot more credence to this answer).
'with' is a charade indicator (letters next to each other).
'death' becomes 'end' (synonyms).
'imp'+'end'='IMPEND'
(Other definitions for impend that I've seen before include "seen to be around the corner" , "Be about to take place" , "Become imminent" , "(Of a bad thing) loom" , "Threaten - be about to happen" .)