Conditioned-reflex researcher (6)
I believe the answer is:
pavlov
'conditioned-reflex researcher' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for pavlov that I've seen before include "Russian who worked with canine responses to food" , "Famous Russian scientist who studied conditioned reflexes in dogs" , "conditioner" , "Russian physiologist noted for studies of canine reflexes" , "Russian investigator of conditioned reflexes" .)