Figures out the tea's stirred, it's milky (5)
I believe the answer is:
latex
But I can't explain it at all! Could you help me understand?
(Other definitions for latex that I've seen before include "Milky fluid produced by plants" , "Milky source of rubber" , "Milky sap of rubber tree" , "Milky fluid from poppies, rubber plants etc" , "white stuff" .)