The most common and most likely answer to this crossword clue is the 6 plus 4 letter word TABULA RASA
I've seen this crossword clue in Financial Times
T
A
B
U
L
A
R
A
S
A
More clues leading to the result TABULA RASA
Buddy explains!

The straight part
We know that "open-minded state" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case open-minded state = tabula rasa.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.