A simple note, say, to translate (4)
I believe the answer is:
easy
'a simple' is the definition.
(I've seen this in another clue)
'note say to translate' is the wordplay.
'note' becomes 'e' (musical note).
'to translate' indicates an anagram.
'say' with letters rearranged gives 'asy'.
'e'+'asy'='EASY'
(Other definitions for easy that I've seen before include "Posing no difficulty" , "Frederick Marryat's midshipman" , "Achieved without effort" , "Comfortable" , "Simply achieved" .)