Make an effort to find the ancestral line (6)
I believe the answer is:
strain
This clue is a double definition.
'make an effort' is the first definition.
(I've seen this before)
'the ancestral line' is the second definition.
(I've seen this in another clue)
'to find' is the link.
(Other definitions for strain that I've seen before include "variety" , "Overwork - melody" , "Trains under stress and pressure" , "Force - melody" , "Muscle injury - tension" .)