The most common and most likely answer to this crossword clue is the 8 letter word FLATLINE
I've seen this crossword clue in The Guardian
F
L
A
T
L
I
N
E
Buddy explains!

The straight part
We know that "come to an end" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case come to an end = flatline.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 FLATLINE mean?
FLATLINE noun- An unchanging state, as indicated in a graph of a variable over time.
- Asystole; the absence of heart contractions or brain waves.
- (of the heart) To stop beating.
- (by extension) To die.
- To kill.
- To stay at the same level, without development; or, to fall.