Family member with article that's impure (7)
I believe the answer is:
unclean
'impure' is the definition.
(I know that impure can be written as unclean)
'family member with article' is the wordplay.
'family member' becomes 'uncle' (brother of a parent).
'with' says to put letters next to each other.
'article' becomes 'an' (English indefinite article).
'uncle'+'an'='UNCLEAN'
'that's' is the link.
(Other definitions for unclean that I've seen before include "Dirty, ritually impure" , "Soiled like an uncle" , "Foul" , "taboo" , "Contaminated" .)