The most common and most likely answer to this crossword clue is the 6 letter word REEKED
I've seen this crossword clue in The Sunday Telegraph
R
E
E
K
E
D
More clues leading to the result REEKED
- Grass-coated hide of elk smelt
- Smelt bad and stretched again!
- I’m afraid boring communist stank
- Scholar abandoned tattered Baedeker that smelt awful
- Wine bottles I say smelt bad
- After eating the last piece of cheese, Derek unfortunately gave off a bad odour
- Communist repressing cry of alarm, created a stink
- Leftie eating endless leeks smelt awful
Buddy explains!

The straight part
We know that "smelt bad" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case smelt bad = reeked.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 REEKED mean?
REEKED verb- To have or give off a strong, unpleasant smell.
- To be evidently associated with something unpleasant.
- To be emitted or exhaled, emanate, as of vapour or perfume.
- To emit smoke or vapour; to steam.