US drab? Wrong, ridiculous (6)
I believe the answer is:
absurd
'ridiculous' is the definition.
('absurd' can be a synonym of 'ridiculous')
'us drab? wrong' is the wordplay.
'wrong' is an anagram indicator.
'us'+'drab'='usdrab'
'usdrab' anagrammed gives 'ABSURD'.
(Other definitions for absurd that I've seen before include "Incredible" , "Really ridiculous, silly" , "Arousing derision" , "Ridiculous, quite nonsensical" , "Highly illogical" .)