The most common and most likely answer to this crossword clue is the 4 letter word FLUB
F
L
U
B
Buddy explains!
The straight part
We know that "error" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case error = flub.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 FLUB mean?
FLUB noun- An error; a mistake in the performance of an action.
- To goof, fumble, or err in the performance of an action.