The most common and most likely answer to this crossword clue is the 9 letter word INGENUITY
I've seen this crossword clue in The Guardian
I
N
G
E
N
U
I
T
Y
Buddy explains!

The straight part
We know that "skill" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case skill = ingenuity.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 INGENUITY mean?
INGENUITY noun- The ability to solve difficult problems, often in original, clever, and inventive ways.
- Ingenuousness; honesty, straightforwardness