Nonsense makes a Norse god run (10)
I believe the answer is:
'nonsense' is the definition.
(balderdash is a kind of nonsense)
'a norse god run' is the wordplay.
'a norse god' becomes 'balder' (Balder is an example).
'run' becomes 'dash' (dash is a kind of run).
'makes' acts as a link.
(Other definitions for balderdash that I've seen before include "tripe" , "Nonsense" , "Senseless talk" , "Poppycock" , "Senseless talk/writing" .)