The most common and most likely answer to this crossword clue is the 6 letter word HORDES
I've seen this crossword clue in The Daily Telegraph
H
O
R
D
E
S
Buddy explains!

The straight part
We know that "Bands" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bands = hordes.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 HORDES mean?
HORDES noun- A wandering troop or gang; especially, a clan or tribe of a nomadic people (originally Tatars) migrating from place to place for the sake of pasturage, plunder, etc.; a predatory multitude.
- A large number of people.