Tribal leader in tree (5)
I believe the answer is:
elder
This clue is a double definition.
'tribal leader' is the first definition.
(I've seen this in another clue)
'tree' is the second definition.
(elder is a kind of tree)
'in' is the link.
(Other definitions for elder that I've seen before include "Senior churchperson" , "Senior tribal figure" , "More ancient" , "Tree for a church senior" , "Senior figure; tree" .)