The most common and most likely answer to this crossword clue is the 8 letter word UNLIKELY
I've seen this crossword clue in Financial Times
U
N
L
I
K
E
L
Y
Buddy explains!

The straight part
We know that "far-fetched" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case far-fetched = unlikely.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 UNLIKELY mean?
UNLIKELY noun- Something or somebody considered unlikely.
- Not likely; improbable; not to be reasonably expected.
- Not holding out a prospect of success; likely to fail; unpromising.
- In an improbable manner.