Has the most expensive eggs in Russia, perhaps? (6)
I believe the answer is:
beluga
I'm afraid I can't even guess how this answer relates to the clue.
Can you help me to learn more?
(Other definitions for beluga that I've seen before include "fish" , "Large sturgeon or it's caviare" , "Species of sturgeon" , "Small white whale; type of caviar" , "Large Russian sturgeon" .)