The most common and most likely answer to this crossword clue is the 4 plus 5 letter word TAKE THAT!
I've seen this crossword clue in The Guardian
T
A
K
E
T
H
A
T
!
Buddy explains!
The straight part
We know that "What’s said to accompany hit/band" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case what’s said to accompany hit/band = take that!.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.