Some considerable time (3)
I believe the answer is:
era
'time' is the definition.
(era is a kind of time)
'some considerable' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'ERA' can be found hidden inside 'considerable'.
(Other definitions for era that I've seen before include "Special time" , "Important time" , "Eon" , "Cycle" , "Series of years" .)