Family crest, inaccurately adopted by some (8)
I believe the answer is:
ancestry
'family' is the definition.
(I've seen this before)
'crest inaccurately adopted by some' is the wordplay.
'inaccurately' indicates anagramming the letters.
'adopted by' indicates putting letters inside (I've seen this in other clues).
'some' becomes 'any' ('any' can be similar in meaning to 'some').
'crest' with letters rearranged gives 'cestr'.
'cestr' placed within 'any' is 'ANCESTRY'.
(Other definitions for ancestry that I've seen before include "Person's ethnic descent" , "Line of forebears" , "race" , "Lineage" , "Genealogy" .)