Plant sap (5)
I believe the answer is:
resin
'plant sap' is the definition.
(I know that plant sap can be written as resin)
This is all the clue.
(Other definitions for resin that I've seen before include "varnish, perhaps" , "Cannabis, say" , "Myrrh, for instance" , "Viscous fluid from tree sap" , "Sticky stuff oozing from trees" .)