Cast away laws (4)
I believe the answer is:
acts
'laws' is the definition.
(I've seen this before)
'cast away' is the wordplay.
'away' indicates anagramming the letters (letters move away from their original places).
'cast' with letters rearranged gives 'ACTS'.
(Other definitions for acts that I've seen before include "Deeds; NT book" , "Religious book" , "Biblical book" , "Dramatic parts" , "Decrees" .)