The most common and most likely answer to this crossword clue is the 13 letter word UNADULTERATED
I've seen this crossword clue in The Daily Telegraph
U
N
A
D
U
L
T
E
R
A
T
E
D
More clues leading to the result UNADULTERATED
- Simple time perhaps for children and youth of the fifties
- Unexpected U-turn with date and deal complete
- A French Blue European judged uncut
- Pure red tea stirred by a French man or woman
- Complete and utter lad dancing with a nude
- Pure, natural duet moving journalist
- A French mature brie finally deemed authentic
- One French man had pot valued to be pure
Buddy explains!
The straight part
We know that "authentic" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case authentic = unadulterated.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 UNADULTERATED mean?
UNADULTERATED adjective- Pure; not mixed or adulterated with anything
- Utter or out-and-out, especially in the phrase unadulterated truth