The most common and most likely answer to this crossword clue is the 6 letter word STENCH
I've seen this crossword clue in Financial Times
S
T
E
N
C
H
More clues leading to the result STENCH
- Strong smell from small fish
- Embrocation finally rubbed into chest – awful stink
- Stink son on Web kicked up, about hackers primarily
- Small catch: there’s no bouquet!
- Nasty smell nauseates ten charge nurses
- Smell comes from small channel, not river
- Starter of smoked fish has strong smell . . . .
- Scores going up to check smell
- Small fish? It may be smelt
- The smell of Sunday’s fish
Buddy explains!
The straight part
We know that "Nasty niff" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case nasty niff = stench.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 STENCH mean?
STENCH noun- A strong foul smell; a stink.
- A foul quality.
- A smell or odour, not necessarily bad.
- To cause to emit a disagreeable odour; to cause to stink.
- To stanch.