Some other age or epoch (3)
I believe the answer is:
era
'epoch' is the definition.
(synonyms)
'some other age or' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'ERA' is hidden within '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" .)