Girl penning info for to-do list (6)
I believe the answer is:
agenda
'to-do list' is the definition.
(to-do list for a meeting)
'girl penning info' is the wordplay.
'girl' becomes 'Ada' (girl's name).
'penning' indicates putting letters inside.
'info' becomes 'gen' (informal term for information).
'ada' placed around 'gen' is 'AGENDA'.
'for' is the link.
(Other definitions for agenda that I've seen before include "Schedule - things to be done" , "List of things to be done or discussed" , "Programme of a meeting" , "List of items for committee to consider" , "Meet to discuss this" .)