Some other age or epoch (3)
I believe the answer is:
era
'epoch' is the definition.
(I know that epoch can be written as era)
'some other age or' is the wordplay.
'some' says the answer is hidden in the clue (some parts of the word are used).
'ERA' can be found hidden inside 'other age or'.
(Other definitions for era that I've seen before include "Characteristic period" , "Long historical period" , "Distinct period in history" , "Important date" , "Age of importance" .)