One in hospital — one needing to be discharged, that’s clear (6)
I believe the answer is:
patent
'clear' is the definition.
(synonyms)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for patent that I've seen before include "Copyright" , "The right to an invention is clear" , "It's registered to protect an invention" , "Open the right to an invention" , "Obvious - protection for inventors" .)