Rest going back in custody at station (4)
I believe the answer is:
stay
'rest' is the definition.
('stay' can be a synonym of 'rest')
'going back in custody at station' is the wordplay.
'going back' shows that the letters should be reversed in order.
'in' indicates a hidden word.
'yats' is hidden in the letters of 'custody at station'.
'yats' in reverse letter order is 'STAY'.
(Other definitions for stay that I've seen before include "Reside" , "Visit (for the night)" , "Don't go!" , "hang about" , "Supporting rod" .)