The most common and most likely answer to this crossword clue is the 9 letter word YORKSHIRE
I've seen this crossword clue in Financial Times
Y
O
R
K
S
H
I
R
E
More clues leading to the result YORKSHIRE
- County dismisses charter
- Henry in danger, back in former times in English region
- Hosiery designed when king’s visiting county
- County once reached by hiker with rosy disposition
- Hosiery designed to clothe kings in old county
- Son missing risky horse sports? Riding was part of it
- Former riding zone is risky, hero getting thrown
- Rosy hiker rambling in northern county
- There’s nothing risky with her new type of pudding
- Duke’s rent from God’s own county!
Buddy explains!
The straight part
We know that "Riding was part of i" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case riding was part of i = yorkshire.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.