The most common and most likely answer to this crossword clue is the 10 letter word SPOILSPORT
I've seen this crossword clue in The Guardian
S
P
O
I
L
S
P
O
R
T
More clues leading to the result SPOILSPORT
Buddy explains!
The straight part
We know that "One ruining the enjoyment of others" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case one ruining the enjoyment of others = spoilsport.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 SPOILSPORT mean?
SPOILSPORT noun- Someone who puts an end to others' fun, especially harmless fun.
- Like a spoilsport.