Decipher, decrypt (6)
I believe the answer is:
decode
I believe this is a double definition.
'decipher' is the first definition.
(I know that decipher can be written as decode)
'decrypt' is the second definition.
(thesaurus)
(Other definitions for decode that I've seen before include "Interpret" , "Decipher, decrypt" , "Get cracking" , "Break a cipher" , "Put in" .)