The most common and most likely answer to this crossword clue is the 3 letter word FEW
I've seen this crossword clue in The Guardian
F
E
W
Buddy explains!
The straight part
We know that "what ‘they’ are in 25’s 4 22" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case what ‘they’ are in 25’s 4 22 = few.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 FEW mean?
FEW pronoun- Few people, few things.