The most common and most likely answer to this crossword clue is the 6 plus 4 letter word SCHOOL BELL
I've seen this crossword clue in Financial Times
S
C
H
O
O
L
B
E
L
L
Buddy explains!
The straight part
We know that "One may signal the end of class/ struggle for youngsters" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one may signal the end of class/ struggle for youngsters = school bell.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.