Long times in the onslaught (4)

I believe the answer is:

eons

'long times' is the definition.
(eon is a kind of long time)

'in the onslaught' is the wordplay.
'in' says the answer is hidden in the clue.
'EONS' is hidden within 'the onslaught'.

(Other definitions for eons that I've seen before include "Times" , "Very long periods (US)" , "Nose (anag)" , "Endless periods" , "Long periods of time - noes have it" .)

I've seen this clue in The Telegraph.

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