Stevenson physician (6)
I believe the answer is:
jekyll
'stevenson physician' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for jekyll that I've seen before include "Doctor with another side to him" , "Hyde's alter ego" , "Famous novel: 'Dr . . . . . . and Mr Hyde'" , "Exact, real" , "The good personality (see 18)" .)