The most common and most likely answer to this crossword clue is the 8 letter word NESCIENT
I've seen this crossword clue in The Daily Telegraph
N
E
S
C
I
E
N
T
More clues leading to the result NESCIENT
Buddy explains!

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 NESCIENT mean?
NESCIENT noun- An ignorant person.
- One who holds that only material phenomena can be known and knowledge of spiritual matters (the unmeasurable) or ultimate causes is impossible.
- Ignorant, unlearned
- Unbelieving