The most common and most likely answer to this crossword clue is the 5 letter word HINNY
H
I
N
N
Y
Buddy explains!
The straight part
We know that "Jock’s darling/cross" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case jock’s darling/cross = hinny.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 HINNY mean?
HINNY noun- The hybrid offspring of a stallion (male horse) and a she-ass (female donkey).
- To whinny
- A term of endearment usually for women.