The most common and most likely answer to this crossword clue is the 7 letter word HAYSEED
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Buddy explains!
The straight part
We know that "Bumpkin" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bumpkin = hayseed.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 HAYSEED mean?
HAYSEED noun- Seeds from grass that has become hay.
- Cruft from bits of hay that sticks to clothing, etc.
- A rustic person; a yokel or bumpkin.
- Characteristic of a hayseed (person).