A mighty long time (4)

I believe the answer is:

ages

'a mighty long time' 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 "Indefinitely long time" , "Long periods" , "A long time (colloq.)" , "Yonks" , "Donkey's years" .)

I've seen this clue in the New York Times.

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