What 1 used get mixed in a pot still, periodically (3,6)
I believe the answer is:
oil paints
'what 1 used' is the definition.
I can't tell whether this definition defines the answer.
'mixed in a pot still periodically' is the wordplay.
'mixed' is an anagram indicator.
'periodically' indicates alternate letters (letters must be selected 'every so often').
The alternating letters of 'still' are 'sil'.
'in'+'a'+'pot'+'sil'='inapotsil'
'inapotsil' is an anagram of 'OIL PAINTS'.
'get' acts as a link.
(Other definitions for oil paints that I've seen before include "What some artists use" , "Artist's pigments" , "Painter's media" , "Artist materials" .)