Descendant or heir (5)
I believe the answer is:
scion
This clue is a double definition.
'descendant' is the first definition.
(I know that scion is a type of descendant)
'heir' is the second definition.
(I've seen this before)
(Other definitions for scion that I've seen before include "Issue" , "Young shoot/twig" , "Branch" , "Young child" , "Younger member of a family" .)