Falsify, adulterate (6)
I believe the answer is:
doctor
This clue is a double definition.
'falsify' is the first definition.
(I've seen this in another clue)
'adulterate' is the second definition.
(I know that doctor is a kind of adulterate)
(Other definitions for doctor that I've seen before include "An apple a day keeps him away" , "Medic or holder of highest university degree" , "Medical specialist" , "Eg, surgeon" , "Medical professional or university don" .)