The most common and most likely answer to this crossword clue is the 4 letter word TODO
T
O
D
O
Buddy explains!
The straight part
We know that "bustle" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bustle = todo.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 TODO mean?
TODO noun- A fuss made over something.
- A task that has been noted as one that must be completed, especially on a list.