.... International vehicle for terrible Russian leader (4)
I believe the answer is:
ivan
'terrible russian leader' is the definition.
(I've seen this in another clue)
'international vehicle' is the wordplay.
'international' becomes 'i' (abbreviation eg in IMF).
'vehicle' becomes 'van' (van is a kind of vehicle).
'i'+'van'='IVAN'
'for' acts as a link.
(Other definitions for ivan that I've seen before include "Vain (anag) - Tsar of Russia" , "his progress in history was terrible!" , "A Terrible old Russian ruler" , "First Russian tsar, 1547-84" , "Name of six Russian tzars" .)