The most common and most likely answer to this crossword clue is the 6 letter word ENGRAM
E
N
G
R
A
M
More clues leading to the result ENGRAM
Buddy explains!

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 ENGRAM mean?
ENGRAM noun- A postulated physical or biochemical change in neural tissue that represents a memory.
- A painful, negative mental image representing a past event.