The most common and most likely answer to this crossword clue is the 9 letter word NO-HOPERS
I've seen this crossword clue in Financial Times
N
O
-
H
O
P
E
R
S
Buddy explains!
The straight part
We know that "Those trailing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case those trailing = no-hopers.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 NO-HOPERS mean?
NO-HOPERS noun- Someone or something that has no hope of success.