Widow has bet after soiree (7)
I believe the answer is:
dowager
'widow' is the definition.
(term for an aristocratic widow)
'bet after soiree' is the wordplay.
'bet' becomes 'wager' (synonyms).
'after' says to put letters next to each other.
'soiree' becomes 'do' (I can't explain this - if you can you should give a lot more credence to this answer).
'wager' after 'do' is 'DOWAGER'.
'has' is the link.
Can you help me to learn more?
(Other definitions for dowager that I've seen before include "Nobleman's widow" , "Widow inheriting husband's title or property" , "Widow with title or property from her husband" , "Widow with inheritance" , "Wordage (anag.)" .)