The most common and most likely answer to this crossword clue is the 6 letter word METTLE
I've seen this crossword clue in Financial Times
M
E
T
T
L
E
More clues leading to the result METTLE
- Satisfied with story overlooking a display of courage
- Police officers let suspect get spirit
- Resolution satisfied ownership of property after it is abandoned
- Loud rock music on Radio Heart
- Police force: “Let’s spread guts!”
- Dictator’s lead perhaps shows courage
- Courage reportedly iron?
- I object to non-drinker seizing the French spirit
- Headbanging music on Radio Heart
- Perhaps lead, we hear, is showing spirit
Buddy explains!

The straight part
We know that "spirit" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case spirit = mettle.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 METTLE mean?
METTLE noun- A quality of endurance and courage.
- Good temperament and character.
- Metal; a metallic substance.