The most common and most likely answer to this crossword clue is the 10 letter word INCOHERENT
I've seen this crossword clue in Financial Times
I
N
C
O
H
E
R
E
N
T
More clues leading to the result INCOHERENT
- Rambling and thin encore done badly
- Neither con breaking loose
- Rambling around Corinth, seen topless
- Difficult to understand nice throne being remodelled
- Rambling in rocky north-east? Nice!
- Confused by intro, hence wandering off
- Elected to learn about present tense, being inarticulate
- Natural to accept cook, oddly, must be rambling
- Innovative thinker once dismissing king not making sense
- Loose company found in natural environment
Buddy explains!

The straight part
We know that "Difficult to understand" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case difficult to understand = incoherent.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 INCOHERENT mean?
INCOHERENT adjective- Not coherent.