The most common and most likely answer to this crossword clue is the 3 plus 6 letter word DOG PADDLE
I've seen this crossword clue in The Guardian
D
O
G
P
A
D
D
L
E
More clues leading to the result DOG PADDLE
Buddy explains!
The straight part
We know that "Stroke" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case stroke = dog paddle.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 DOG PADDLE mean?
DOG PADDLE noun- A swimming stroke in the style of a dog swimming.
- To swim using the dog paddle stroke.