The most common and most likely answer to this crossword clue is the 4 letter word REEK
I've seen this crossword clue in Financial Times
R
E
E
K
More clues leading to the result REEK
- Hum — create sounds like this
- Stink in river that’s frightening
- Stink when classical language gets its first cut
- European losing final in ping pong
- Stench from burn about to disappear
- Hum when tough vocabulary’s no good
- . Start of record I’m frightened to hum
- Smack in Staffordshire town changing hands
- Smoke half of joint, then kip
- Reportedly cause terrible smell
Buddy explains!

The straight part
We know that "a strong smell" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a strong smell = reek.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 REEK mean?
REEK noun- A strong unpleasant smell.
- Vapour; steam; smoke; fume.
- 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.
- A hill; a mountain.