She can decipher from French business overdrawn returns (7)
I believe the answer is:
decoder
'she can decipher' is the definition.
I can't judge whether this definition defines the answer.
'from french business overdrawn returns' is the wordplay.
'from french' becomes 'de' ('from' in French).
'business' becomes 'co' (short for company).
'overdrawn returns' becomes 'der' (I am not sure about this - if you are sure you should believe this answer much more).
'de'+'co'+'der'='DECODER'
Can you help me to learn more?
(Other definitions for decoder that I've seen before include "One interpreting cipher" , "The interpreter" , "Data converter" , "This person decrypts" , "Eg, digital to analogue converter" .)