Adult in employment suffering setback — one giving away a basic right (4)
I believe the answer is:
esau
'one giving away a basic right' is the definition.
(reference to the Biblical character)
'adult in employment suffering setback' is the wordplay.
'adult' becomes 'a'.
'in' indicates putting letters inside.
'employment' becomes 'use' ('use' can be a synonym of 'employment').
'suffering setback' says the letters should be written in reverse.
'a' put into 'use' is 'uase'.
'uase' in reverse letter order is 'ESAU'.
(Other definitions for esau that I've seen before include "Jacob's brother (Gen.)" , "Biblical character sounds as if he had a vision" , "Hairy OT man" , "man tricked by kid brother" , "wronged brother" .)