Improves, as wine
I believe the answer is:
ages
'improves as wine' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ages that I've seen before include "Epochs" , "... of Man, according to WB Yeats" , "(What seems) a very long time" , "A long time (colloq.)" , "Times" .)