The most common and most likely answer to this crossword clue is the 9 letter word SPALPEENS
I've seen this crossword clue in The Guardian
S
P
A
L
P
E
E
N
S
Buddy explains!

The straight part
We know that "Rascals" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rascals = spalpeens.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 SPALPEENS mean?
SPALPEENS noun- A poor migratory farm worker in Ireland, often viewed as a rascal or mischievous and cunning person.
- (sometimes affectionate) A good-for-nothing person.