The most common and most likely answer to this crossword clue is the 8 letter word POLEAXED
I've seen this crossword clue in The Daily Telegraph
P
O
L
E
A
X
E
D
More clues leading to the result POLEAXED
Buddy explains!
The straight part
We know that "Caused great shock to" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case caused great shock to = poleaxed.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 POLEAXED mean?
POLEAXED verb- To fell someone with, or as if with, a poleaxe.
- To astonish; to shock or surprise utterly.