The most common and most likely answer to this crossword clue is the 4 letter word LETT
I've seen this crossword clue in The Guardian
L
E
T
T
Buddy explains!

The straight part
We know that "one from eastern Europe" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one from eastern europe = lett.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 LETT mean?
LETT verb- To allow to, not to prevent (+ infinitive, but usually without to).
- To leave.
- To allow the release of (a fluid).
- To allow possession of (a property etc.) in exchange for rent.
- To give, grant, or assign, as a work, privilege, or contract; often with out.
- Used to introduce an imperative in the first or third person.
- To cause (+ bare infinitive).
- To hinder, prevent, impede, hamper, cumber; to obstruct (someone or something).
- To prevent someone from doing something; also to prevent something from happening.
- To tarry or delay.