The most common and most likely answer to this crossword clue is the 8 letter word CLAYMORE
I've seen this crossword clue in Independent
C
L
A
Y
M
O
R
E
More clues leading to the result CLAYMORE
- About to put down extra for sword
- Old fighter added old weapon
- Objective at heart? To do extra setting is mine!
- Master follows amateur into interior with weapon
- Sword put by leader of Macdonalds into heart
- Weapon, something fired further
- Blade’s about to become increasingly promiscuous?
- Royal mace brandished but not a sword
- College to offer additional weapon
- Ali once requiring extra weapon
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 CLAYMORE mean?
CLAYMORE noun- A large two-handed sword historically used by the Scottish Highlanders.
- Alternative letter-case form of Claymore (antipersonnel mine)