The most common and most likely answer to this crossword clue is the 7 letter word PRINTER
I've seen this crossword clue in The Daily Telegraph
P
R
I
N
T
E
R
Buddy explains!
The straight part
We know that "who makes an impression" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case who makes an impression = printer.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 PRINTER mean?
PRINTER noun- One who makes prints.
- The operator of a printing press, or the owner of a printing business.
- A device, usually attached to a computer, used to print text or images onto paper; an analogous device capable of producing three-dimensional objects.