Root, derivation (6)
I believe the answer is:
origin
This clue is a double definition.
'root' is the first definition.
(I know that root can be written as origin)
'derivation' is the second definition.
(I know that origin is a type of derivation)
(Other definitions for origin that I've seen before include "Where one begins" , "For a start" , "Genesis" , "Source, derivation" , "extraction" .)