The most common and most likely answer to this crossword clue is the 8 letter word ABORTIVE
I've seen this crossword clue in The Daily Telegraph
A
B
O
R
T
I
V
E
More clues leading to the result ABORTIVE
- Failed riverboat broken up without resistance
- Steal show outside, returning fruitless
- Backing musical about Sting, in vain
- Failed to use a bit over for recycling
- Unsuccessful trio pulled apart by a book have to take a 50 per cent cut
- Unsuccessful person on board, one tackled by furious voter
- Oddly a bit over-idle?
- Unsuccessful over a bit falling apart
Buddy explains!

The straight part
We know that "Unsuccessful" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case unsuccessful = abortive.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 ABORTIVE mean?
ABORTIVE noun- That which is born or brought forth prematurely; an abortion.
- A fruitless effort or issue.
- A medicine to which is attributed the property of causing abortion, abortifacient.
- To cause an abortion; to render without fruit.
- Produced by abortion; born prematurely and therefore unnatural.
- Coming to nothing; failing in its effect; miscarrying; fruitless; unsuccessful.
- Imperfectly formed or developed; rudimentary; sterile.
- (pharmaceutical effect) Causing abortion; abortifacient
- Cutting short; acting to halt or slow the progress (of a disease).
- Made from the skin of a still-born animal.