The most common and most likely answer to this crossword clue is the 10 letter word BOOBY-TRAP
I've seen this crossword clue in The Times
B
O
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B
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More clues leading to the result BOOBY-TRAP
Buddy explains!
The straight part
We know that "In military terms, prime" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case in military terms, prime = booby-trap.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 BOOBY-TRAP mean?
BOOBY-TRAP noun- An antipersonnel device deliberately hidden or disguised as a harmless object.
- A practical joke by which something is made to fall upon someone entering through a door, or the like.
- (by extension) An unforeseen source of danger; a pitfall.
- To set up with booby traps; to plant a booby trap on.