The most common and most likely answer to this crossword clue is the 5 letter word REEKS
I've seen this crossword clue in The Times
R
E
E
K
S
More clues leading to the result REEKS
- Europeans denied their capital stinks
- Hums number ones of recent era
- Run – I’m scared opening of Surströmming will produce unpleasant smells
- Foul smells left opening of Scotsman’s trousers
- Smells Europeans first off
- … exhales from occasionally briefer kiss
- Butt of cigar ekes out smokes
- Hums song, principally after sex, getting alarmed expression
- Resistance to cries of fear – that stinks!
- Regressive soothsayer stifles king's odors
Buddy explains!

The straight part
We know that "Hums" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case hums = reeks.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 REEKS mean?
REEKS 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.