18a. Cigar-smoking ragamuffin in group doctor brought back (5). I have S?T?N.
20a. European in XL pants is a Pulitzer-prize winner (1,5,6). I have E ?N?I? P?O?L?. I'm fairly certain about the initial single E as it's from 13d (CHESTERTON) but there again I've often been over-confident.