Former lover is a vacuous talker and an open, outgoing person (9)
I believe the answer is:
extrovert
'outgoing person' is the definition.
(I've seen this before)
'former lover is a vacuous talker and an open' is the wordplay.
'former lover' becomes 'ex' (ex-lover).
'is a vacuous talker' becomes 'tr' (I can't explain this - if you can you should give a lot more credence to this answer).
'and' says to put letters next to each other.
'an open' becomes 'overt' (I've seen this before).
'ex'+'tr'+'overt'='EXTROVERT'
Can you help me to learn more?
(Other definitions for extrovert that I've seen before include "Person who is more interested in the world than the inner self" , "Outgoing rather than inward-looking" , "he's turned out" , "party animal" , "party type" .)