Twain preteen (6)
I believe the answer is:
sawyer
'twain preteen' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for sawyer that I've seen before include "Boy hero of Mark Twain's novel" , "Huckleberry Finn's friend Tom ___" , "Tom or Bob has been booked?" , "Fictional Tom" , "Mark Twain wrote 'The Adventures of Tom . . . . . .'" .)