The most common and most likely answer to this crossword clue is the 8 letter word LANDMINE
I've seen this crossword clue in The Guardian
L
A
N
D
M
I
N
E
More clues leading to the result LANDMINE
Buddy explains!
The straight part
We know that "explosive device" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case explosive device = landmine.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 LANDMINE mean?
LANDMINE noun- A mine that is placed on land and designed to explode when stepped upon or touched.
- To sow (an area) with land mines.