The most common and most likely answer to this crossword clue is the 13 letter word HALLUCINATORY
I've seen this crossword clue in The Daily Telegraph
H
A
L
L
U
C
I
N
A
T
O
R
Y
Buddy explains!

The straight part
We know that "producing visions?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case producing visions? = hallucinatory.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.
Crossword Answer definitions
HALLUCINATORY adjective- Partaking of, or tending to produce, hallucination.