The most common and most likely answer to this crossword clue is the 8 letter word UNSEATED
U
N
S
E
A
T
E
D
Buddy explains!
The straight part
We know that "Luckless rider may be" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case luckless rider may be = unseated.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 UNSEATED mean?
UNSEATED verb- To throw from one's seat; to deprive of a seat.
- To deprive of the right to sit in a legislative body, as for fraud in election, or simply by defeating them in an election.
- Not seated.