The most common and most likely answer to this crossword clue is the 4 letter word JAKE
J
A
K
E
More clues leading to the result JAKE
Buddy explains!

The straight part
We know that "US bumpkin/honest" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case us bumpkin/honest = jake.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 JAKE mean?
JAKE noun- A juvenile male turkey.
- Police, a federal government officer.
- A police officer (on foot, rather than in a patrol car)
- Jamaica ginger
- A Discordian prank involving a large number of people sending bizarre letters or parcels to a targeted individual.
- To play a Discordian prank on (somebody), involving a large number of people sending bizarre letters or parcels to that person.
- Adequate; satisfactory; acceptable.