Defoe's castaway (6)
I believe the answer is:
crusoe
'defoe's castaway' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for crusoe that I've seen before include "Shipwrecked hero" , "Defoe's hero derived" , "shipwrecked fellow" , "See 9" , "Robinson on the island" .)