Veto taking over year to satisfy one abroad (7)
I believe the answer is:
nullify
'veto' is the definition.
(veto can mean to nullify or invalidate)
'over year to satisfy one abroad' is the wordplay.
'over' says the letters should be written in reverse.
'year' becomes 'y'.
'to satisfy' becomes 'fill' (synonyms).
'one abroad' becomes 'un' (French for 'one' - when abroad).
'y'+'fill'+'un'='yfillun'
'yfillun' reversed gives 'NULLIFY'.
'taking' acts as a link.
(Other definitions for nullify that I've seen before include "Declare invalid" , "quash" , "Bring to naught" , "Make of no effect" , "Make void" .)