Bit of money entertaining American relative (6)
I believe the answer is:
cousin
'relative' is the definition.
(I know that cousin is a type of relative)
'bit of money entertaining american' is the wordplay.
'bit of money' becomes 'coin'.
'entertaining' is an insertion indicator (inviting in, as for dinner).
'american' becomes 'US' (abbreviation for United States).
'coin' going around 'us' is 'COUSIN'.
(Other definitions for cousin that I've seen before include "person once removed?" , "Relation, could be kissing" , "Family relation" , "Address used among sovereigns" , "Family relative" .)