The most common and most likely answer to this crossword clue is the 10 letter word UNREALISED
U
N
R
E
A
L
I
S
E
D
Buddy explains!
The straight part
We know that "not yet met" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case not yet met = unrealised.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 UNREALISED mean?
UNREALISED adjective- Not realized; possible to obtain or achieve, yet not obtained or achieved.