The most common and most likely answer to this crossword clue is the 8 letter word DECENTLY
I've seen this crossword clue in The Daily Telegraph
D
E
C
E
N
T
L
Y
More clues leading to the result DECENTLY
Buddy explains!

The straight part
We know that "in proper fashion" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case in proper fashion = decently.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 DECENTLY mean?
DECENTLY adverb- In a decent manner.
- To a reasonable or acceptable degree.