The most common and most likely answer to this crossword clue is the 7 letter word EIDOLON
I've seen this crossword clue in The Guardian
E
I
D
O
L
O
N
Buddy explains!

The straight part
We know that "Image" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case image = eidolon.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 EIDOLON mean?
EIDOLON noun- An image or representation of an idea; a representation of an ideal form; an apparition of some actual or imaginary entity, or of some aspect of reality.
- A phantom, a ghost or elusive entity.