Note after journey is nonsense (5)
I believe the answer is:
tripe
'is nonsense' is the definition.
(informal term for nonsense or false information)
'note after journey' is the wordplay.
'note' becomes 'e' (musical note).
'after' means one lot of letters go next to another.
'journey' becomes 'trip' (trip is a kind of journey).
'e' put after 'trip' is 'TRIPE'.
(Other definitions for tripe that I've seen before include "Pants" , "Cow's stomach lining used as food" , "Swallowed" , "Rubbish; offal" , "poor stuff" .)