The most common and most likely answer to this crossword clue is the 3 plus 3 plus 3 plus 5 letter word OUT FOR THE COUNT
I've seen this crossword clue in Financial Times
O
U
T
F
O
R
T
H
E
C
O
U
N
T
Buddy explains!
The straight part
We know that "As van Helsing/as van Winkel" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case as van helsing/as van winkel = out for the count.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.