Unadulterated (4)
I believe the answer is:
pure
'unadulterated' is the definition.
(I know that unadulterated can be written as pure)
This is all the clue.
(Other definitions for pure that I've seen before include "Not mixed or adulterated" , "Nothing but; innocent" , "Unalloyed" , "Undefiled" , "free of bad grammar" .)