The most common and most likely answer to this crossword clue is the 5 letter word RONIN
I've seen this crossword clue in Financial Times
R
O
N
I
N
More clues leading to the result RONIN
Buddy explains!
The straight part
We know that "Lordless swordsman" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case lordless swordsman = ronin.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 RONIN mean?
RONIN noun- A masterless samurai (who often becomes a mercenary to make ends meet).
- (in Japan) A student who has failed the entrance examination for the high school or university of their choice: if the student does not wish to take the exam the following year or is unable to, the student becomes a ronin, assuming full responsibility for their own training and survival.