I go deeper leaving nothing out in family tree (8)
I believe the answer is:
Here is my best explanation:
'family tree' is the definition.
(pedigree is a kind of family tree)
'i go deeper leaving nothing out' is the subsidiary indication.
'leaving' suggests deleting specific letters.
'nothing' becomes 'o' (looks like zero - 0).
'out' is an anagram indicator.
'igodeeper' with 'o' removed is 'igdeeper'.
'igdeeper' anagrammed gives 'pedigree'.
'in' is the link.
(Other definitions for pedigree that I've seen before include "(Distinguished) lineage", "Ancestry of a purebred animal", "Thoroughbred", "Line of ancestry, particularly a distinguished one", "Line of ancestors", "Ancestry, lineage", "record", "High-class", "Lineage of purebred animal" and "Stock".)