Proper drink I have, being unsophisticated (9)
I believe the answer is:
primitive
'being unsophisticated' is the definition.
(thesaurus)
'proper drink i have' is the wordplay.
'proper' becomes 'prim' (prim and proper).
'drink' becomes 'it'.
'i have' becomes 'I've' (contraction of 'I have').
'prim'+'it'+'ive'='PRIMITIVE'
(Other definitions for primitive that I've seen before include "Early - simple - crude" , "Original - uncivilised" , "Ancient" , "extremely basic" , "As artist Rousseau was e" .)