The most common and most likely answer to this crossword clue is the 4 letter word YOCK
Y
O
C
K
Buddy explains!
The straight part
We know that "some laughter in theatre" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case some laughter in theatre = yock.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 YOCK mean?
YOCK noun- A laugh, especially a loud or hearty one.
- To laugh, especially loudly or uproariously