Grows older (4)
I believe the answer is:
ages
'grows older' is the definition.
('age' can be a synonym of 'grow older')
This is the entire clue.
(Other definitions for ages that I've seen before include "A long time (colloq.)" , "Epochs" , "... of Man, according to WB Yeats" , "Rock of - - (hymn)" , "Yonks" .)