The most common and most likely answer to this crossword clue is the 8 letter word LIFESPAN
I've seen this crossword clue in The Guardian
L
I
F
E
S
P
A
N
More clues leading to the result LIFESPAN
- How long one might be?
- Fine pals excited in every minute of existence
- Psychic power in strange final period of existence
- Terribly false pride originally in existence
- In the time between life and death, self-pain is absurd
- Total duration of pain
- Fine spa destroyed after 50 years of existence
- Biography to encompass one’s entire existence
Buddy explains!

The straight part
We know that "every minute of existence" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case every minute of existence = lifespan.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 LIFESPAN mean?
LIFESPAN noun- The length of time for which an organism lives.
- (by extension) The length of time for which something exists or is current or valid.