The most common and most likely answer to this crossword clue is the 9 letter word OUTERMOST
I've seen this crossword clue in The Guardian
O
U
T
E
R
M
O
S
T
More clues leading to the result OUTERMOST
Buddy explains!

The straight part
We know that "farthest away" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case farthest away = outermost.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 OUTERMOST mean?
OUTERMOST adjective- Outside; external.
- Farther from the centre of the inside.
- That which is outermost; the surface; the outside.