Gibberish, nonsense (5,5)
I believe the answer is:
mumbo jumbo
I believe this clue is a double definition.
'gibberish' is the first definition.
(I know that mumbo jumbo is a type of gibberish)
'nonsense' is the second definition.
(I know that mumbo jumbo is a type of gibber)
(Other definitions for mumbo jumbo that I've seen before include "Ritual intercourse" , "obscure language" , "Gobbledegook" , "Mysterious speech" , "Claptrap" .)