Not in code, note hidden in cake (2,5)
I believe the answer is:
en clair
'not in code' is the definition.
(I've seen this before)
'note hidden in cake' is the wordplay.
'note' becomes 'n' (abbreviation).
'hidden in' is an insertion indicator.
'cake' becomes 'eclair' (I've seen this before).
'n' going into 'eclair' is 'EN CLAIR'.
(Other definitions for en clair that I've seen before include "in ordinary language" , "It's easy to get" , "Not in cipher" , "in the Open" , "in understandable form" .)