The most common and most likely answer to this crossword clue is the 12 letter word LILLIPUTIANS
I've seen this crossword clue in The Daily Telegraph
L
I
L
L
I
P
U
T
I
A
N
S
More clues leading to the result LILLIPUTIANS
Buddy explains!

The straight part
We know that "Swift people" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case swift people = lilliputians.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 LILLIPUTIANS mean?
LILLIPUTIANS noun- A very small person or being.
- (genetics) A fruit fly gene that, when mutated, makes cells abnormally small. See AFF2.