Norse god to frustrate stupid talk (10)
I believe the answer is:
balderdash
'stupid talk' is the definition.
(I've seen this before)
'norse god to frustrate' is the wordplay.
'norse god' becomes 'balder' (Balder is an example).
'to frustrate' becomes 'dash' (I've seen this before).
'balder'+'dash'='BALDERDASH'
(Other definitions for balderdash that I've seen before include "cobblers > GAME" , "Claptrap" , "Poppycock" , "tripe" , "rot" .)