Threaten new conflict first (4)
I believe the answer is:
warn
'threaten' is the definition.
(I've seen this in another clue)
'new conflict first' is the wordplay.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'conflict' becomes 'war' (war is a kind of conflict).
'first' says to put 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" .)