Rinse out sap (5)
I believe the answer is:
Here is my best explanation:
'sap' is the definition.
(I've seen this before)
'rinse out' is the subsidiary indication.
'out' is an anagram indicator.
'rinse' with letters rearranged gives 'resin'.
(Other definitions for resin that I've seen before include "It exudes from pines", "Tree exudation", "Plant exudation", "Organic polymer used in varnishes, adhesives etc.", "Substance from tree-sap", "Elemi, for example", "Sticky tree exudation", "Sap product", "Rinse out this substance from trees" and "Lac".)