The most common and most likely answer to this crossword clue is the 6 letter word YAWING
I've seen this crossword clue in The Daily Telegraph
Y
A
W
I
N
G
Buddy explains!
The straight part
We know that "flying erratically" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case flying erratically = yawing.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 YAWING mean?
YAWING verb- To turn about the vertical axis while maintaining course.
- To swerve off course to port or starboard.
- To steer badly, zigzagging back and forth across the intended course of a boat; to go out of the line of course.
- To rise in blisters, breaking in white froth, as cane juice in the clarifiers in sugar works.