The most common and most likely answer to this crossword clue is the 6 letter word RAGMAN
R
A
G
M
A
N
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The straight part
We know that "Second-hand dealer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case second-hand dealer = ragman.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 RAGMAN mean?
RAGMAN noun- A person who collects and sells unwanted household items such as rags and other refuse for a living, a rag and bone man.
- A statute issued by Edward I in 1276.
- A document having many names or seals, such as a papal bull.
- A game in which players compete to pull an object from out of a roll of writing.