Relation puts us in the money (6)
I believe the answer is:
cousin
'relation' is the definition.
(I know that relation can be written as cousin)
'us in the money' is the wordplay.
'in the' means one lot of letters goes inside another.
'money' becomes 'coin' (I've seen this before).
'us' placed inside 'coin' is 'COUSIN'.
'puts' is the link.
(Other definitions for cousin that I've seen before include "An uncle or aunt's child" , "Relation, could be kissing" , "Son or daughter of an uncle or aunt" , "Close relative" , "Child of a parent's sibling, say" .)