I will leave Russian front (3)
I believe the answer is:
van
'front' is the definition.
(I've seen this in other clues)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for van that I've seen before include "Leading part" , "Leading point of army" , "Leading unit at the head of an army" , "Pantechnicon" , "Light lorry" .)