The most common and most likely answer to this crossword clue is the 11 letter word GRAVEDIGGER
I've seen this crossword clue in The Times
G
R
A
V
E
D
I
G
G
E
R
More clues leading to the result GRAVEDIGGER
Buddy explains!
The straight part
We know that "Unsmiling Australian working in churchyard" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case unsmiling australian working in churchyard = gravedigger.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 GRAVEDIGGER mean?
GRAVEDIGGER noun- A person employed to dig graves.
- A necrophore, or burying beetle.