The most common and most likely answer to this crossword clue is the 7 letter word SECRECY
I've seen this crossword clue in Independent
S
E
C
R
E
C
Y
Buddy explains!

The straight part
We know that "concealed state" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case concealed state = secrecy.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 SECRECY mean?
SECRECY noun- Concealment; the condition of being secret or hidden.
- The habit of keeping secrets.