The most common and most likely answer to this crossword clue is the 15 letter word RESURRECTIONIST
I've seen this crossword clue in Independent
R
E
S
U
R
R
E
C
T
I
O
N
I
S
T
Buddy explains!
The straight part
We know that "Hare?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case hare? = resurrectionist.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.