Elder, for example, in family diagram (4)
I believe the answer is:
tree
I believe this is a double definition.
'elder for example' is the first definition.
(elder is a kind of tree)
'family diagram' is the second definition.
(I've seen this in another clue)
'in' acts as a link.
(Other definitions for tree that I've seen before include "Christmas decoration" , "Shoe stretcher" , "Birch, say" , "Diagram representing different relationships" , "Branching diagram" .)