The most common and most likely answer to this crossword clue is the 8 letter word PHANTOMS
I've seen this crossword clue in Independent
P
H
A
N
T
O
M
S
More clues leading to the result PHANTOMS
Buddy explains!

The straight part
We know that "visions" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case visions = phantoms.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 PHANTOMS mean?
PHANTOMS noun- A ghost or apparition.
- Something apparently seen, heard, or sensed, but having no physical reality; an image that appears only in the mind; an illusion or delusion.
- A placeholder for a pair of players when there are an odd number of pairs playing.
- (medical imaging) A test object.