Unknown newly formed tribunal protects tree (6,3)
I believe the answer is:
brazil nut
'tree' is the definition.
(brazil nut is a kind of tree)
'unknown newly formed tribunal protects' is the wordplay.
'unknown' becomes 'z' (algebra).
'newly formed' indicates an anagram.
'protects' means one lot of letters goes inside another (outer letters protect inside letters).
'tribunal' with letters rearranged gives 'brailnut'.
'z' inserted inside 'brailnut' is 'BRAZIL NUT'.
(Other definitions for brazil nut that I've seen before include "Edible seed from South America" , "Fruit with a shell - run a blitz (anag)" , "it's hard to swallow" , "source of protein" , "that's hard to crack?" .)