The most common and most likely answer to this crossword clue is the 8 letter word HUMORIST
I've seen this crossword clue in Independent
H
U
M
O
R
I
S
T
Buddy explains!
The straight part
We know that "Who could give /us/us/ mirth, nothing more?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case who could give /us/us/ mirth, nothing more? = humorist.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 HUMORIST mean?
HUMORIST noun- Someone who believes that health and temperament are determined by bodily humours; a humoralist.
- Someone subject to whims or fancies.
- A humorous or witty person, especially someone skilled in humorous writing or performance.
- One who studies or portrays the humours of people.