Weapon came off (4)
I believe the answer is:
mace
'weapon' is the definition.
'came off' is the wordplay.
'off' indicates anagramming the letters.
'came' is an anagram of 'MACE'.
(Other definitions for mace that I've seen before include "Spice from the nutmeg seed" , "Came to get ceremonial staff" , "Came to get ancient weapon" , "Came to find ceremonial staff" , "One of 9 [CLUBS]" .)