Weapons of smart, mean design (9)
I believe the answer is:
armaments
'weapons' is the definition.
(I've seen this before)
'smart mean design' is the wordplay.
'design' indicates an anagram.
'smart'+'mean'='smartmean'
'smartmean' anagrammed gives 'ARMAMENTS'.
'of' acts as a link.
(Other definitions for armaments that I've seen before include "Weapons for men-at-arms" , "Munitions" , "Military weaponry" .)