Money stopped by American relative (6)
I believe the answer is:
cousin
'relative' is the definition.
(I know that cousin is a type of relative)
'money stopped by american' is the wordplay.
'money' becomes 'coin' (coin is a type of money).
'stopped by' means one lot of letters goes inside another (stopping can mean blocking a gap).
'american' becomes 'US' (abbreviation for United States).
'coin' enclosing 'us' is 'COUSIN'.
(Other definitions for cousin that I've seen before include "Relation, could be kissing" , "Son or daughter of an uncle or aunt" , "Child of a parent's sibling, say" , "Aunt's/uncle's child" , "person once removed?" .)