Get older and change plan for meeting (6)
I believe the answer is:
agenda
'plan for meeting' is the definition.
(I've seen this before)
'get older and change' is the wordplay.
'get older' becomes 'age' (synonyms).
'change' is an anagram indicator.
'and' with letters rearranged gives 'nda'.
'age'+'nda'='AGENDA'
(Other definitions for agenda that I've seen before include "Items of business for committee meeting" , "Matters to be addressed" , "List of matters to be discussed at a meeting" , "Programme of business" , "List of business for a committee meeting" .)