It's not right to be abandoned (4)
I believe the answer is:
left
I believe this is a double definition.
'it's not right' is the first definition.
('left' is the opposite to 'right')
'be abandoned' is the second definition.
(leave can mean to abandon)
'to' acts as a link.
(Other definitions for left that I've seen before include "The sinister side" , "It's not right" , "choice at a junction?" , "Departed, went away" , "political group" .)