The most common and most likely answer to this crossword clue is the 11 letter word CLAIRVOYANT
I've seen this crossword clue in The Times
C
L
A
I
R
V
O
Y
A
N
T
More clues leading to the result CLAIRVOYANT
- Cavalry not deployed to arrest one visionary
- Actor vainly playing a fortune teller
- Bad actor vainly looking at the future
- Seer vainly involved with actor
- Seeing the future of a vicar only upset them initially
- Medium crayon vital for editing?
- Unusually gifted person originally ordered into cavalry
- Broken crayon vital for one who makes 3s
Buddy explains!

The straight part
We know that "visionary" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case visionary = clairvoyant.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 CLAIRVOYANT mean?
CLAIRVOYANT noun- A person able to see things that cannot be perceived by the normal senses.
- A person able to foresee the future.
- Of or relating to clairvoyance.
- Able to see things that cannot be perceived by the normal senses.
- Able to foresee the future.
- Relating to a form of parallel processing algorithm given advance information about the problem.