The most common and most likely answer to this crossword clue is the 5 letter word EMBUS
I've seen this crossword clue in The Times
E
M
B
U
S
Buddy explains!

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 EMBUS mean?
EMBUS verb- To put (troops) onto a bus
- To board a bus