The most common and most likely answer to this crossword clue is the 8 letter word NEOTERIC
I've seen this crossword clue in The Guardian
N
E
O
T
E
R
I
C
Buddy explains!

The straight part
We know that "modern/modern" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case modern/modern = neoteric.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 NEOTERIC mean?
NEOTERIC noun- A modern author (especially as opposed to a classical writer).
- Someone with new or modern ideas.
- Modern, new-fangled.
- New; recent.