The most common and most likely answer to this crossword clue is the 2 plus 3 plus 4 letter word ON THE BALL
I've seen this crossword clue in Independent
O
N
T
H
E
B
A
L
L
More clues leading to the result ON THE BALL
- Where to place billiards cue, being alert?
- Alert, looking to pass or shoot?
- Monthstarts off with everyone alert
- Quick to respond, getting one’s kicks?
- Alert to where eight may be in pool
- Dribbling on one’s toes?
- Informed about article ahead of social event
- Alert and effective playing soccer, say?
- Alert to position of soccer sponsor’s logo
- Informed about article on Liberal party getting withdrawn
Buddy explains!

The straight part
We know that "Alert to/where eight may be in pool" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case alert to/where eight may be in pool = on the ball.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.