The most common and most likely answer to this crossword clue is the 13 letter word QUALIFICATION
I've seen this crossword clue in Financial Times
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More clues leading to the result QUALIFICATION
Buddy explains!
The straight part
We know that "Rider’/skill" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rider’/skill = qualification.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 QUALIFICATION mean?
QUALIFICATION noun- The act or process of qualifying for a position, achievement etc.
- An ability or attribute that aids someone's chances of qualifying for something; specifically, completed professional training.
- A certificate, diploma, or degree awarded after successful completion of a course, training, or exam.
- A clause or condition which qualifies something; a modification, a limitation.
- A quality or attribute.