A French veto soon (4)
I believe the answer is:
anon
'soon' is the definition.
(I've seen this before)
'a french veto' is the wordplay.
'french veto' becomes 'non' (French for 'no', a word which might veto something).
'a'+'non'='ANON'
(Other definitions for anon that I've seen before include "prolific author" , "soon to be written" , "Soon; unattributed" , "Soon, in a little while" , "Soon or presently" .)