The most common and most likely answer to this crossword clue is the 12 letter word EXPERIMENTAL
I've seen this crossword clue in The Daily Telegraph
E
X
P
E
R
I
M
E
N
T
A
L
More clues leading to the result EXPERIMENTAL
- Trial of old fairy getting ridiculous
- Fellows supporting one in authority with a line that’s tentative
- Old fairytale being intellectual? Not yet fully proved
- Refined male, expert in avant-garde
- Ace, almost one intellectual pilot
- Erstwhile beautiful female gets mad trying out new styles
- On trial, professional gangster admits detonating mine
- Head of investigative personnel involved in ace gangster’s trial
- Specialist detailed one ridiculous trial
- Tentative old fairy at a sort of arithmetic?
Buddy explains!
The straight part
We know that "Not yet fully proved" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case not yet fully proved = experimental.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 EXPERIMENTAL mean?
EXPERIMENTAL noun- The subject of an experiment.
- Pertaining to or founded on experiment.
- Serving to be experimented upon; used in an experiment.
- Serving as an experiment; serving to experiment.
- Experiential, empirical.