Rubber basis (5)
I believe the answer is:
latex
'rubber basis' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for latex that I've seen before include "Rubbery juice" , "Milky substance from rubber tree" , "Synthetic product" , "Juice in rubber-making" , "Milky substance produced by some trees" .)