The most common and most likely answer to this crossword clue is the 8 letter word INGENUES
I've seen this crossword clue in The Daily Telegraph
I
N
G
E
N
U
E
S
Buddy explains!

The straight part
We know that "Naive young things" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case naive young things = ingenues.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 INGENUES mean?
INGENUES noun- An innocent, unsophisticated, naïve, wholesome girl or young woman.
- A dramatic role of such a woman; an actress playing such a role.