The most common and most likely answer to this crossword clue is the 8 letter word SUPEREGO
I've seen this crossword clue in The Guardian
S
U
P
E
R
E
G
O
More clues leading to the result SUPEREGO
- Group seem endlessly flummoxed by this Freudian concept
- Poseur failing to hide, for example, unconscious inhibitor
- See group struggling, having conscience in mind
- Mind part of drink before journey
- Head of Germany, Europe’s troubled conscience
- Leader of Greece pricking Europe’s uneasy conscience
- Some personality, for example, in eccentric poseur
- Drink before you leave with confidence
- Head of Germany, Europe's troubled conscience
- Dine before travel showing moral conscience
Buddy explains!

The straight part
We know that "Mind part" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mind part = superego.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 SUPEREGO mean?
SUPEREGO noun- The part of the mind that acts as a self-critical conscience, reflecting social standards that have been learnt.