Senseless, fatuous (8)
I believe the answer is:
mindless
I believe this clue is a double definition.
'senseless' is the first definition.
(I know that senseless can be written as mindless)
'fatuous' is the second definition.
(synonyms)
(Other definitions for mindless that I've seen before include "Acting with no concern for the consequences" , "Irrational" , "(Of activity) repetitive and simple" , "Acting unthinkingly" , "Silly" .)