The most common and most likely answer to this crossword clue is the 7 letter word RISIBLE
I've seen this crossword clue in The Times
R
I
S
I
B
L
E
More clues leading to the result RISIBLE
- Hilarious bishop is rising in anger
- Comic brother or sister consumed by anger
- Twice jumping up when bitten by bug? That's ludicrous
- Master turning up to scripture topless is absurd
- Iberis spread across lake? That’s ludicrous
- Ludicrous to provoke outstanding relative
- Ridiculous bug has overwhelmed relative
- Source of ruin in sight — not very funny
- One pound kept back in pay increase? That’s ridiculous
- Absurd anger consuming brother, say
Buddy explains!

The straight part
We know that "Hilarious" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case hilarious = risible.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 RISIBLE mean?
RISIBLE adjective- Of or pertaining to laughter
- Provoking laughter; ludicrous; ridiculous; humorously insignificant
- (of a person) Easily laughing; prone to laughter