The most common and most likely answer to this crossword clue is the 9 letter word INCESSANT
I've seen this crossword clue in The Guardian
I
N
C
E
S
S
A
N
T
More clues leading to the result INCESSANT
- Constant crime around odd parts of Spain
- Odd instances happening all the time
- Trendy twit rolling in money, never stopping
- Endless popular ascents to go up
- Small article involved in illegal relationship that’s on-going
- Unfortunate instances, uninterrupted
- Endless botched instances
- Awfully nice saint — saint losing heart or keeping going?
- Uninterrupted in various instances
- Eternal taboo broken by the first of seven angry neurologists
Buddy explains!

The straight part
We know that "happening all the time" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case happening all the time = incessant.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 INCESSANT mean?
INCESSANT adjective- Without pause or stop; not ending, especially to the point of annoyance.