Balderdash, nonsense (6)
I believe the answer is:
piffle
I believe this clue is a double definition.
'balderdash' is the first definition.
(I know that balderdash can be written as piffle)
'nonsense' is the second definition.
(I know that nonsense can be written as piffle)
(Other definitions for piffle that I've seen before include "Rubbish, nonsense" , "rot" , "Cock" , "Hogwash" , "Trivial nonsense" .)