The most common and most likely answer to this crossword clue is the 14 letter word KNIGHTS-ERRANT
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Buddy explains!
The straight part
We know that "old cavaliers" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case old cavaliers = knights-errant.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 KNIGHTS-ERRANT mean?
KNIGHTS-ERRANT noun- A knight in a medieval romance who wanders in search of adventure and opportunities to prove his chivalry.
- A person who displays an adventurous or a quixotic spirit.