The most common and most likely answer to this crossword clue is the 2 plus 4 letter word ON SIDE
I've seen this crossword clue in The Sunday Telegraph
O
N
S
I
D
E
Buddy explains!
The straight part
We know that "OK to receive ball" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ok to receive ball = on side.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 ON SIDE mean?
ON SIDE adjective- Not in an offside position; In the part of the playing area where one can legally play the ball, puck, etc.
- On the side of a vehicle from which the driver, paddler, etc. propels it.
- Favourably located, from the point of view of the player taking a finesse.
- In agreement or support; on board.