The most common and most likely answer to this crossword clue is the 5 plus 4 letter word STINK BOMB
I've seen this crossword clue in The Guardian
S
T
I
N
K
B
O
M
B
More clues leading to the result STINK BOMB
- Liquidin small vault whence pong emanates
- Black mass comes together to raise something with foul content
- Small burial chamber containing writing material, book and source of foul smell
- Furore with turkey as practical joke
- Move quickly after trouble caused by prankster’s device
- Practical joke involving high explosive?
- Rotating ties aren’t popular joke shop purchase
- Gang joins retiring bishop making toy weapon
- It smells awful when it goes off
- Furore over fortune seeing one with a nasty smell
Buddy explains!
The straight part
We know that "source of foul smell" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case source of foul smell = stink bomb.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.