Disabled and unsound (7)
I believe the answer is:
invalid
I believe this clue is a double definition.
'disabled' is the first definition.
(I've seen this before)
'unsound' is the second definition.
(similar in meaning)
'and' is the link.
(Other definitions for invalid that I've seen before include "Having no effect" , "patient [found]" , "Nullified" , "Flawed" , "Not true" .)