Influential American wants one of Groucho's kin sent into retirement (5)
I believe the answer is:
oprah
'influential american' is the definition.
(Oprah Winfrey)
'one of groucho's kin sent into retirement' is the wordplay.
'one of groucho's kin' becomes 'Harpo' (Harpo Marx, brother of Groucho Marx).
'sent into retirement' says the letters should be written in reverse (retire can mean to go back).
'harpo' backwards is 'OPRAH'.
'wants' is the link.
(Other definitions for oprah that I've seen before include "- - Winfrey (TV)" , "American chat show host" , "Chat show queen" , "Miss Winfrey" .)