The most common and most likely answer to this crossword clue is the 8 plus 7 letter word BASEBALL DIAMOND
I've seen this crossword clue in The Guardian
B
A
S
E
B
A
L
L
D
I
A
M
O
N
D
Buddy explains!
The straight part
We know that "Pitches on this" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case pitches on this = baseball diamond.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.