The most common and most likely answer to this crossword clue is the 8 letter word PREVIEWS
P
R
E
V
I
E
W
S
Buddy explains!

The straight part
We know that "trailers" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case trailers = previews.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 PREVIEWS mean?
PREVIEWS noun- An experience of something in advance.
- An advance showing of a film, exhibition etc.
- Something seen in advance.
- A facility for seeing and checking a document, or changes to it, before saving and/or printing it.
- To show or watch something, or part of it, before it is complete.