The most common and most likely answer to this crossword clue is the 5 letter word ENNUI
I've seen this crossword clue in The Guardian
E
N
N
U
I
More clues leading to the result ENNUI
- Tedium starts to exhaust now nothing usually interests
- During endless tennis, universal boredom
- Boredom seen in pupil regularly
- Boredom is the heart of genuine upset
- Nine drunk around university in a state of boredom
- Seen insulin regularly used for tiredness
- Boredom to an extent rotten nuisance
- In most of night in Paris, showing listlessness
- News in Brussels on current malaise
- All sent one quiz, essentially it’s boredom
Buddy explains!

The straight part
We know that "malaise" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case malaise = ennui.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 ENNUI mean?
ENNUI noun- A gripping listlessness or melancholia caused by boredom; depression.
- To make bored or listless; to weary.