Reject; refuse (4)
I believe the answer is:
deny
I believe this clue is a double definition.
'reject' is the first definition.
(I know that deny is a more specific form of the action disown)
'refuse' is the second definition.
(I know that refuse can be written as deny)
(Other definitions for deny that I've seen before include "Refuse to admit the truth" , "contest" , "Disown" , "Declare non-existent" , "Gainsay" .)