The most common and most likely answer to this crossword clue is the 2 plus 7 letter word IN EARNEST
I've seen this crossword clue in The Sunday Telegraph
I
N
E
A
R
N
E
S
T
More clues leading to the result IN EARNEST
- Seriously, I’m almost home
- I close venue for undesirables urgently
- Meaningfully I get close to den
- Seriously, two homes require internal attention
- One shelter in which to make money seriously
- Train seen moving purposefully
- Individual approaching home with zeal
- Seriously bad trainees found around Norway
- One close to retreat is resolute
- One close to home is not joking
Buddy explains!

The straight part
We know that "properly" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case properly = in earnest.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.