Car retained by some in support payment (7)
I believe the answer is:
alimony
'support payment' is the definition.
(alimony is a kind of support payment)
'car retained by some' is the wordplay.
'car' becomes 'limo' (limo is a kind of car).
'retained by' is an insertion indicator.
'some' becomes 'any' (similar in meaning).
'limo' put into 'any' is 'ALIMONY'.
'in' is the link.
(Other definitions for alimony that I've seen before include "Compensation awarded by court to divorced person" , "divorce arrangement" , "Divorce payment" , "Allowance due to be paid after separation" , "Court-ordered maintenance" .)