Senior — tree (5)
I believe the answer is:
elder
I believe this clue is a double definition.
'senior' is the first definition.
(I know that senior can be written as elder)
'tree' is the second definition.
(elder is a kind of tree)
(Other definitions for elder that I've seen before include "sort of statesman" , "Tree and Mormon church officer" , "Official of some Churches, or senior statesman" , "Senior churchman - shrub" , "Senior tribal figure" .)