The most common and most likely answer to this crossword clue is the 8 letter word INCOMING
I've seen this crossword clue in The Times
I
N
C
O
M
I
N
G
Buddy explains!

The straight part
We know that "arriving on the scene" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case arriving on the scene = incoming.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 INCOMING mean?
INCOMING noun- The act of coming in; arrival.
- Enemy fire directed at oneself.
- Coming (or about to come) in; arriving.
- Succeeding to an office.
- A warning that something is coming towards you; especially enemy artillery fire