Man finally delving into poor Tracey’s lineage (8)
I believe the answer is:
ancestry
'lineage' is the definition.
('ancestry' can be a synonym of 'lineage')
'man finally delving into poor tracey's' is the wordplay.
'finally' suggests the final letters.
'delving into' means one lot of letters goes inside another.
'poor' is an anagram indicator.
The final letter of 'man' is 'n'.
'traceys' anagrammed gives 'acestry'.
'n' put inside 'acestry' is 'ANCESTRY'.
(Other definitions for ancestry that I've seen before include "Any crest (anag.)" , "Lineage" , "race" , "Line of forebears" , "Line of descendants" .)