Repeal brought up in jail, unnaturally (5)
I believe the answer is:
annul
'repeal' is the definition.
('annul' can be a synonym of 'repeal')
'brought up in jail unnaturally' is the wordplay.
'brought up' says the letters should be written backwards (down clues only).
'in' indicates the answer is hidden within the clue.
'lunna' is hidden within 'jail unnaturally'.
'lunna' backwards is 'ANNUL'.
(Other definitions for annul that I've seen before include "Declare void" , "Cancel officially" , "Cancel, revoke" , "Cancel, make void" , "Nullify" .)