The most common and most likely answer to this crossword clue is the 9 letter word ENDURANCE
I've seen this crossword clue in The Daily Telegraph
E
N
D
U
R
A
N
C
E
More clues leading to the result ENDURANCE
- Staying power of English knight Mussolini managed to get imprisoned
- Result united country without force or lasting power
- Last to be first in this test!
- Ran nude around church, showing stamina
- In French disco, perhaps, you are said to join in, showing stamina
- Finish first ultra marathon heartened by new stamina
- Prue powerless with canned bananas’ stickability
- Complete university competition after injection of new stamina
- Lasting quality in unearned cash primarily inauthentic
- Staying power needed to finish university career, gaining first in nanotechnology
Buddy explains!

The straight part
We know that "stamina" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case stamina = endurance.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 ENDURANCE mean?
ENDURANCE noun- The measure of a person's stamina or persistence.
- Ability to endure hardship.
- The length of time that a ship's rations will supply