An aged spinster, but she's game! (3,4)
I believe the answer is:
old maid
'game' is the definition.
(I know that Old maid is a type of card game)
'an aged spinster but she's' is the wordplay.
I cannot really see how this works, but
'an' could be 'i' (Roman numeral for one) and 'i' is located in the answer.
'aged' could be 'old' (similar in meaning) and 'old' is present in the answer.
The remaining letters 'mad' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for old maid that I've seen before include "She's elderly and unmarried" , "Excessively cautious person" , "Singleton" , "game of cards" , "Spinster - card game" .)