The most common and most likely answer to this crossword clue is the 6 letter word HAZING
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More clues leading to the result HAZING
Buddy explains!

The straight part
We know that "bullying" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bullying = hazing.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 HAZING mean?
HAZING verb- To be or become hazy, or thick with haze.
- To perform an unpleasant initiation ritual upon a usually non-consenting individual, especially freshmen to a closed community such as a college or military unit.
- To oppress or harass by forcing to do hard and unnecessary work.
- In a rodeo, to assist the bulldogger by keeping (the steer) running in a straight line.
- An initiation or behavior that involves humiliation, harassment or abuse, particularly in universities and in the military.