Original and influential (7)
I believe the answer is:
seminal
'original and influential' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for seminal that I've seen before include "Highy important" , "Strongly influencing future developments" , "Generating new developments for menials" , "Groundbreaking" , "Very important, original" .)