Form or make up (10)
I believe the answer is:
constitute
I believe this is a double definition.
'form' is the first definition.
(I know that form can be written as constitute)
'make up' is the second definition.
(I know that make up can be written as constitute)
(Other definitions for constitute that I've seen before include "Make up" , "Found" , "Be (a part) of a whole" , "form" .)