Unclear about weapons (7)
I believe the answer is:
nuclear
'weapons' is the definition.
(I have seen 'powerful weapons' mean 'nuclear' so perhaps 'weapons' could also mean 'nuclear')
'unclear about' is the wordplay.
'about' is an anagram indicator.
'unclear' anagrammed gives 'NUCLEAR'.
(Other definitions for nuclear that I've seen before include "These weapons release atomic energy" , "Like some physics" , "type of power supply" , "source of energy" , "> certain WMDs" .)