The most common and most likely answer to this crossword clue is the 12 letter word FOREQUARTERS
I've seen this crossword clue in The Times
F
O
R
E
Q
U
A
R
T
E
R
S
More clues leading to the result FOREQUARTERS
Buddy explains!

The straight part
We know that "stud's leading part?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case stud's leading part? = forequarters.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 FOREQUARTERS mean?
FOREQUARTERS noun- The foreleg, shoulder and surrounding area of the body of a quadruped.
- The front half of a side of meat.