Proprietary - that's very clear (6)
I believe the answer is:
patent
'clear' is the definition.
(synonyms)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for patent that I've seen before include "The invention protection is obvious" , "easily accessible" , "The right to an invention is clear" , "Obvious, unconcealed" , "Registration of ownership of invention" .)