Neat, undiluted (4)
I believe the answer is:
pure
I believe this is a double definition.
'neat' is the first definition.
(both can mean undiluted)
'undiluted' is the second definition.
(synonyms)
(Other definitions for pure that I've seen before include "Untainted" , "Undefiled" , "Virginal" , "Not mixed or adulterated" , "Not mixed with anything else" .)