The most common and most likely answer to this crossword clue is the 8 letter word WEBSITES
I've seen this crossword clue in The Daily Telegraph
W
E
B
S
I
T
E
S
Buddy explains!
The straight part
We know that "where trolls will not be welcome" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case where trolls will not be welcome = websites.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 WEBSITES mean?
WEBSITES noun- A collection of interlinked web pages on the World Wide Web that are typically accessible from the same base URL and reside on the same server.