Rub ads out? That's nonsensical (6)
I believe the answer is:
absurd
'that's nonsensical' is the definition.
(synonyms)
'rub ads out?' is the wordplay.
'out?' is an anagram indicator (I've seen 'out' mean this (out can mean wrong or inaccurate)).
'rub'+'ads'='rubads'
'rubads' anagrammed gives 'ABSURD'.
(Other definitions for absurd that I've seen before include "irrational" , "Patently ridiculous" , "Wildly illogical" , "Ridiculous, illogical" , "Incredible" .)