Girl in game ultimately lost (7)
I believe the answer is:
bridget
'girl' is the definition.
'game ultimately lost' is the wordplay.
'game' becomes 'bridge' (bridge is a kind of game).
'ultimately lost' becomes 't' (I can't justify this - if you can you should give a lot more credence to this answer).
'bridge'+'t'='BRIDGET'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for bridget that I've seen before include "Saint" , "Girl" , "Miss Jones the diarist" , "Saintly woman" .)