Terrible Russian providing one with transport (4)
I believe the answer is:
ivan
'terrible russian' is the definition.
(Ivan the Terrible)
'one with transport' is the wordplay.
'one' becomes 'an' (an apple is one apple).
'with' means one lot of letters go next to another.
'transport' becomes 'iv' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'an' put after 'iv' is 'IVAN'.
'providing' acts as a link.
Can you help me to learn more?
(Other definitions for ivan that I've seen before include "terrible tyrant" , "A Russian emperor, quite Terrible" , "First Russian tsar, 1547-84" , "Russian, say" , "- - the Terrible (Czar)" .)