The most common and most likely answer to this crossword clue is the 4 plus 3 plus 5 letter word KNOW THE SCORE
I've seen this crossword clue in The Sunday Telegraph
K
N
O
W
T
H
E
S
C
O
R
E
More clues leading to the result KNOW THE SCORE
- People following match will understand the situation
- Understand — as should a conductor?
- Understand what’s what — as might professional musician?
- Be informed, as should an orchestral musician?
- A tennis umpire should be well-informed?
- Rehearsed orchestral players will appreciate the situation
- Harry chose network to be well informed
- Be aware of the facts as to how many runs have been made?
- What one on fiddle must do to be clear about situation?
Buddy explains!
The straight part
We know that "Understand what’s what" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case understand what’s what = know the score.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.