Henry __, Edward Hyde's better half? (6)
I believe the answer is:
jekyll
(Other definitions for jekyll that I've seen before include "Robert Louis Stevenson novel 'Dr . . . . . . and Mr Hyde'" , "Famous novel 'Dr ...... and Mr Hyde'(6) ()" , "The good personality (see 18)" , "Doctor with an alter ego" , "Exact, real" .)