Grow older (3)
'grow older' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for get on that I've seen before include "Advance; prosper" , "Make progress; be friends" , "Enjoy harmonious relationship" , "Proceed; prosper" , "Board (a bus)" .)
'grow older' is the definition.
(synonyms)
This is all the clue.
(Other definitions for age that I've seen before include "16/18 [INDUSTRIAL REVOLUTION]" , "Get old" , "Length of life" , "Epoch" , "Turkish commander" .)