Of one's forebears (9)
I believe the answer is:
ancestral
'of one's forebears' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ancestral that I've seen before include "To do with forebears, say stately home" , "of predecessors" , "handed down by family" , "To do with forebears from Lancaster" , "Coming down the line" .)