Fatuous, silly (5)
I believe the answer is:
inane
I believe this is a double definition.
'fatuous' is the first definition.
(I know that fatuous can be written as inane)
'silly' is the second definition.
(I've seen this in another clue)
(Other definitions for inane that I've seen before include "Frivolous" , "Daft" , "Annie (anag.)" , "Empty-headed" , "Lacking meaning" .)