The most common and most likely answer to this crossword clue is the 6 letter word POSEUR
I've seen this crossword clue in The Daily Telegraph
P
O
S
E
U
R
More clues leading to the result POSEUR
- One who’s affected position over Europe
- Post Office sure upset pretentious type
- Show-off taking problem round university
- Someone trying to impress regrets surgery after uplift
- Regrets surgery adversely affected individual
- Exhibitionist in French street, thus quietly revolting
- Problem involving upper-class person acting insincerely
- Pretentious type is sorry for work backfiring
- Exhibitionist regrets work being sent up
- Exhibitionist rose up flashing
Buddy explains!

The straight part
We know that "Exhibitionist" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case exhibitionist = poseur.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 POSEUR mean?
POSEUR noun- One who affects some behaviour, style, attitude or other condition, often to impress or influence others.