With 57-Across, savings plan with tax-free withdrawals (4)
I believe the answer is:
roth
(Other definitions for roth that I've seen before include "Philip --, US author" , "Portnoy's Complaint author, d. 2018" , "American Jewish novelist, Philip, b. 1933" , "Author of Portnoy's Complaint, b. 1933" , "American writer" .)