The most common and most likely answer to this crossword clue is the 2 plus 2 letter word ET TU
E
T
T
U
More clues leading to the result ET TU
Buddy explains!
The straight part
We know that "Brute went after this, murderously" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case brute went after this, murderously = et tu.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.