The most common and most likely answer to this crossword clue is the 6 plus 4 letter word ARTHUR ASHE
A
R
T
H
U
R
A
S
H
E
More clues leading to the result ARTHUR ASHE
Buddy explains!
The straight part
We know that "A renowned tennis hero; universally respected American sportsman; his excellence spotted early on?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a renowned tennis hero; universally respected american sportsman; his excellence spotted early on? = arthur ashe.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.