Agricultural chemical from tea tree (6)
I believe the answer is:
potash
'agricultural chemical' is the definition.
(I've seen this before)
'tea tree' is the wordplay.
'tea' becomes 'pot' (I am not sure about this - if you are sure you should believe this answer much more).
'tree' becomes 'ash' (ash is a kind of tree).
'pot'+'ash'='POTASH'
'from' acts as a link.
Can you help me to learn more?
(Other definitions for potash that I've seen before include "The strange pathos of a potassium compound" , "Compound used in agriculture and industry - shop at (anag)" , "Alkaline compound" , "Strong alkali derived from burnt wood" , "Powerful alkali from burnt wood" .)