Grow old and supply to-do list (6)
I believe the answer is:
agenda
'to-do list' is the definition.
(to-do list for a meeting)
'grow old and supply' is the wordplay.
'grow old' becomes 'age' (synonyms).
'supply' indicates an anagram (in a supple way).
'and' is an anagram of 'nda'.
'age'+'nda'='AGENDA'
(Other definitions for agenda that I've seen before include "Business to be transacted" , "things still to be done" , "Something perhaps hidden" , "Topic list for meeting" , "things to discuss" .)