Stupid; senseless (7)
I believe the answer is:
asinine
I believe this is a double definition.
'stupid' is the first definition.
(I've seen this before)
'senseless' is the second definition.
(I've seen this before)
(Other definitions for asinine that I've seen before include "Stupid (as a donkey?)" , "In the nature of supposedly stupid animal" , "Really silly, ridiculous" , "Extremely stupid or foolish" , "Silly like a donkey" .)