The most common and most likely answer to this crossword clue is the 12 letter word ASTONISHMENT
I've seen this crossword clue in The Daily Telegraph
A
S
T
O
N
I
S
H
M
E
N
T
More clues leading to the result ASTONISHMENT
- Disbelief as regarding one's Queen visiting shelter
- Concerning the province, “quiet” meant avoiding a surprise
- Shock pastor inwardly, with odd hints about primates
- Is the Queen arriving in Birmingham university hospital dept causing surprise?
- Half of Brummie FC players wearing this spoilt surprise
- Mean host isn’t prepared for shock
- Criminal man’s honest? It creates confusion
- Doctor Sam on this hospital dept creating surprise
- University is hard — chaps finally admit shock
- Disbelief on account of ten months lost overcoming infection’s onset
Buddy explains!

The straight part
We know that "shock" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case shock = astonishment.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 ASTONISHMENT mean?
ASTONISHMENT noun- The feeling or experience of being astonished; great surprise.
- Something very surprising.
- Loss of physical sensation; inability to move a part of the body.
- Loss of mental faculties, inability to think or use one's senses.
- Loss of composure or presence of mind.