The most common and most likely answer to this crossword clue is the 4 letter word HICK
H
I
C
K
More clues leading to the result HICK
Buddy explains!

The straight part
We know that "Rustic" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rustic = hick.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 HICK mean?
HICK noun- An awkward, naive, clumsy and/or rude country person.
- To hiccup