Figure to finish duty at an advanced age (6)
I believe the answer is:
ninety
'an advanced age' is the definition.
'ninety' can be an answer for 'age' (I have seen 'old age' mean 'ninety' so perhaps 'age' could also mean 'ninety'). I am not sure about the 'an advanced' bit.
'figure to finish duty' is the wordplay.
'figure' becomes 'nine' (I've seen this in other clues).
'to finish duty' becomes 'ty' (I can't justify this - if you can you should believe this answer much more).
'nine'+'ty'='NINETY'
'at' acts as a link.
Can you help me to learn more?
(Other definitions for ninety that I've seen before include "''Oh, the craic was ... in the Isle of Man'' (The Dubliners)" , "Cardinal" , ""Top of the shop" in bingo" , "XC (in ancient Rome)" , "Figure in inn, yet, strangely" .)