Long, long times (4)
'long long times' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for eons that I've seen before include "Divisions of geological time" , "Divisions of archaeological time" , "Years and years" , "Very long periods (US)" , "Long periods of time - noes have it" .)
(Other definitions for aeons that I've seen before include "Vast ages" , "Long periods of time" .)