Widow has bet after party (7)
I believe the answer is:
dowager
'widow' is the definition.
(I know that dowager is a type of widow)
'bet after party' is the wordplay.
'bet' becomes 'wager' (synonyms).
'after' means one lot of letters go next to another.
'party' becomes 'do' (do is a kind of party).
'wager' put after 'do' is 'DOWAGER'.
'has' acts as a link.
(Other definitions for dowager that I've seen before include "Rich old girl" , "woman of status" , "woman of property?" , "Widow, imposing elderly woman" , "Titled widow" .)