Adhesive setting for tooth and tongue (3,6)
I believe the answer is:
gum arabic
'adhesive' is the definition.
'setting for tooth and tongue' is the wordplay.
'setting for tooth' becomes 'gum'.
'and' is a charade indicator (letters next to each other).
'tongue' becomes 'arabic' (Arabic is an example).
'gum'+'arabic'='GUM ARABIC'
(Other definitions for gum arabic that I've seen before include "Exudation used in glues and incense" , "Ingredient of 16 across" , "Substance exuded by acacia" , "glue" .)