Strange crest dividing a New York family (8)
I believe the answer is:
ancestry
'family' is the definition.
(I've seen this before)
'strange crest dividing a new york' is the wordplay.
'strange' indicates anagramming the letters.
'dividing' indicates putting letters inside.
'new york' becomes 'ny'.
'crest' anagrammed gives 'cestr'.
'a'+'ny'='any'
'cestr' put into 'any' is 'ANCESTRY'.
(Other definitions for ancestry that I've seen before include "Blood line" , "Person's ethnic descent" , "Family tree" , "Lineage" , "Any crest (anag.)" .)