The most common and most likely answer to this crossword clue is the 4 plus 5 letter word PEER GROUP
I've seen this crossword clue in The Guardian
P
E
E
R
G
R
O
U
P
More clues leading to the result PEER GROUP
- People like you to look adult, not callow again, ultimately
- Those of the same class – upper class?
- Contemporaries who are normally found around Duchamp’s fountain?
- Classmates, say, look intently at Greek press
- People similar to one noble rise when king enters
- Classmates or upper-class mates?
- Contemporaries of Duke, say, scramble to protect Harry’s heart
Buddy explains!
The straight part
We know that "Classmates" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case classmates = peer group.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.