Chief, primary (4)
I believe the answer is:
main
I believe this is a double definition.
'chief' is the first definition.
(I know that chief can be written as main)
'primary' is the second definition.
(I know that primary can be written as main)
(Other definitions for main that I've seen before include "river in Germany" , "Most important or greatest in size" , "Most important element" , "Foremost" , "Cardinal" .)