The most common and most likely answer to this crossword clue is the 9 letter word IMPRINTED
I've seen this crossword clue in Independent
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More clues leading to the result IMPRINTED
Buddy explains!

The straight part
We know that "Impressed" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case impressed = imprinted.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 IMPRINTED mean?
IMPRINTED verb- To leave a print, impression, image, etc.
- To learn something indelibly at a particular stage of life, such as who one's parents are.
- To mark a gene as being from a particular parent so that only one of the two copies of the gene is expressed.
- Stamped or impressed.
- Produced by or exhibiting imprinting; showing distinction by its origin from the paternal or maternal genome.