White substance provided as one preparing joint? (9)
I believe the answer is:
alabaster
'white substance' is the definition.
(I've seen this before)
'as one preparing joint?' is the wordplay.
'as' becomes 'ala' (French 'a la' - 'in the style of').
'one preparing joint?' becomes 'baster' (somebody basting).
'ala'+'baster'='ALABASTER'
'provided' is the link.
(Other definitions for alabaster that I've seen before include "White substance" , "White stone carved into ornaments" , "medium of sculpture" , "Altar base (anag)" , "White or translucent mineral" .)