Thus ape correct writer's protection (9)
I believe the answer is:
'writer's protection' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'thus ape correct' is the wordplay.
I cannot quite understand how this works, but
'ape' could be 'copy' (synonyms) and 'copy' is found in the answer.
'correct' could be 'right' (right can mean correct) and 'right' is found in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for copyright that I've seen before include "legal protection against piracy" , "property of the author?" , "control publication" , "Document granting exclusive right to publish" , "Protected" .)