The most common and most likely answer to this crossword clue is the 3 letter word WOW
I've seen this crossword clue in Independent
W
O
W
Buddy explains!

The straight part
We know that "Bowl over" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bowl over = wow.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 WOW mean?
WOW noun- Anything exceptionally surprising, unbelievable, outstanding, etc.
- To amaze or awe.
- An indication of excitement, surprise, astonishment, or pleasure.
- An expression of amazement, awe, or admiration.
- Used sarcastically to express disapproval of something.
- (audio) A relatively slow form of flutter (pitch variation) which can affect both gramophone records and tape recorders.