The most common and most likely answer to this crossword clue is the 8 letter word TSARINAS
I've seen this crossword clue in The Guardian
T
S
A
R
I
N
A
S
Buddy explains!
The straight part
We know that "group of top Russians" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case group of top russians = tsarinas.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does TSARINAS mean?
TSARINAS noun- An empress of several Eastern European countries, especially Russia, or the wife of a tsar.