The most common and most likely answer to this crossword clue is the 7 letter word ZONKING
I've seen this crossword clue in Financial Times
Z
O
N
K
I
N
G
Buddy explains!

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 ZONKING mean?
ZONKING verb- To hit hard .
- To make (someone) sleepy or delirious, to put into a stupor .
- (usually followed by “out”) To become exhausted, sleepy or delirious.
- Striking; great.