The most common and most likely answer to this crossword clue is the 4 plus 2 plus 3 plus 7 letter word PUSH UP THE DAISIES
I've seen this crossword clue in The Times
P
U
S
H
U
P
T
H
E
D
A
I
S
I
E
S
Buddy explains!
The straight part
We know that "to have been buried" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case to have been buried = push up the daisies.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.