The most common and most likely answer to this crossword clue is the 5 plus 3 plus 2 plus 5 letter word CLOSE BUT NO CIGAR
I've seen this crossword clue in The Sunday Telegraph
C
L
O
S
E
B
U
T
N
O
C
I
G
A
R
More clues leading to the result CLOSE BUT NO CIGAR
- Conservative icon gets Labour rattled, almost
- Leader in city, urban ecologist unfortunately just failing
- Counterfeit tobacco ruling covering Home Counties almost successful
- Winston, when intimate and divested of habit, just not managing it
- Almost tame gnus eat broccoli!
- Extremely sensitive tobacco ruling out? Not quite there
Buddy explains!
The straight part
We know that "just failing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case just failing = close but no cigar.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.