The most common and most likely answer to this crossword clue is the 7 letter word ZIPPERS
I've seen this crossword clue in The Daily Telegraph
Z
I
P
P
E
R
S
Buddy explains!
The straight part
We know that "ones that move fast" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ones that move fast = zippers.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 ZIPPERS mean?
ZIPPERS noun- A zip fastener.
- A pressure-sensitive plastic closure.
- Leucine zipper
- A scar on a person's body.
- An air patrol carried out at dawn or dusk.
- To close a zipper.
- To put a zipper on an article.