Threaten new conflict first (4)
I believe the answer is:
warn
'threaten' is the definition.
(thesaurus)
'new conflict first' is the wordplay.
'new' becomes 'n'.
'conflict' becomes 'war' (war is a kind of conflict).
'first' is a charade indicator (letters next to each other).
'n' after 'war' is 'WARN'.
(Other definitions for warn that I've seen before include "Make aware of danger" , "Tip off" , "Admonish, caution" , "Alert" , "Give advance notice to" .)