Peterkin —, survivor, with Ralph Rover and Jack Martin, of a shipwreck in R M Ballantyne novel The Coral Island (3)
I believe the answer is:
gay
(Other definitions for gay that I've seen before include "Merry" , "Homosexual" , "John --, author of 'The Beggar's Opera'" , "Writer of The Beggar's Opera" , "Light-hearted, carefree" .)