The most common and most likely answer to this crossword clue is the 9 letter word UNTRODDEN
I've seen this crossword clue in Independent
U
N
T
R
O
D
D
E
N
Buddy explains!

The straight part
We know that "EastEnders/where no one has been" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case eastenders/where no one has been = untrodden.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 UNTRODDEN mean?
UNTRODDEN adjective- That has never been trod upon; unexplored, unspoiled.
- Of a person: undefeated.