Heaven is the end of many a Russian (3)
I believe the answer is:
sky
'heaven' is the definition.
(I've seen this in another clue)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for sky that I've seen before include "Strike up" , "Hit (a ball) very high" , "Hit upwards" , "Weather" , "Hit high into the air" .)