They talk a lot about fights involving mad member of party (12)

'they' is the definition.
Both the answer and definition are plural nouns.
Maybe they are linked in a way I don't understand?

'talk a lot about fights involving mad member of party' is the wordplay.
I cannot quite see how this works, but
'talk' could be 'chatter' (chattering is a kind of talking) and 'chatter' is found in the answer.
'fights' could be 'boxes' and 'boxes' is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...

Can you help me to learn more?