The most common and most likely answer to this crossword clue is the 4 letter word ZONK
Z
O
N
K
More clues leading to the result ZONK
Buddy explains!

The straight part
We know that "Hit" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case hit = zonk.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 ZONK mean?
ZONK noun- An unfavorable card or token, or undesirable or worthless item used as a prize in a contest or game show (such as Let's Make a Deal).
- A feeling of a drug taking hold.
- To hit hard .
- To make (someone) sleepy or delirious, to put into a stupor .
- (usually followed by “out”) To become exhausted, sleepy or delirious.