The most common and most likely answer to this crossword clue is the 8 letter word STINKING
I've seen this crossword clue in The Daily Telegraph
S
T
I
N
K
I
N
G
More clues leading to the result STINKING
Buddy explains!

The straight part
We know that "Fetid" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fetid = stinking.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 STINKING mean?
STINKING verb- To have a strong bad smell.
- To be greatly inferior; to perform badly.
- To give an impression of dishonesty or untruth.
- To cause to stink; to affect by a stink.
- Having a pungent smell.
- Very bad and undesirable.
- An intensifier, a minced oath.
- The emission of a foul smell.