First-born tribal leader (5)
I believe the answer is:
elder
This clue is a double definition.
'first-born' is the first definition.
(I've seen this before)
'tribal leader' is the second definition.
(I've seen this in another clue)
(Other definitions for elder that I've seen before include "Tree and Mormon church officer" , "Official of some Churches, or senior statesman" , "one with roots" , "Senior member - plant" , "Small tree with purple berries" .)