Inception director may be found here (5)
I believe the answer is:
onset
'inception' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
(Other definitions for onset that I've seen before include "Beginning (of something often unpleasant)" , "Beginning (of disease etc)" , "Start - opening moments" , "Beginning; military attack" , "Start - attack" .)