Flawed United Nations measure (7)
I believe the answer is:
unsound
'flawed' is the definition.
(I've seen this before)
'united nations measure' is the wordplay.
'united nations' becomes 'un' ('UN' can be a synonym of 'united nations').
'measure' becomes 'sound' (sounding is a kind of measuring**).
'un'+'sound'='UNSOUND'
(Other definitions for unsound that I've seen before include "Ill-founded" , "Being crazy, sort of mind" , "Rotten; bad (argument)" , "Faulty" , "Not strong or free from defect - perhaps evidence in court" .)