The most common and most likely answer to this crossword clue is the 5 plus 3 plus 2 plus 3 plus 4 letter word EIGHT OUT OF TEN CATS
I've seen this crossword clue in The Guardian
E
I
G
H
T
O
U
T
O
F
T
E
N
C
A
T
S
Buddy explains!
The straight part
We know that "Panel show" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case panel show = eight out of ten cats.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.